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My V-King came with the fuel tank in the front.
There is evidence it was once in the back.
I suspect it was moved to the front when the the boat was repowered to a Yamaha.
The Yami included an oil tank and a hydraulic jack plate with a remote pump and reservoir.
In short, I don't think it fit in the back. It is a 19 USG aluminum deal.

What are the pros and cons of having the fuel tank in the front?
When the fuel tank is in the back, does it cover the sump where the bilge pump goes?
Do knee braces create issues for tank placement?

I saw one build where splash well area was extended forward. Creating more space in the rear. Interesting.

I saw somewhere that it is "stupid" to put the fuel tank in the front.
A little harsh, but his opinion was clear.
He didn't give any reasons.
What is the prevailing theory?
Maybe put it in the front if you have a big heavy 4 stroke on the back?
I will be sticking with 2 stroke for as long as practical.

Yes, in a performance boat such as the Hydrostream, putting a gas tank up front is absolutely stupid. The reason is, it is not static weight so if you have a full tank up front and the bow is really heavy, it could either handle very poor, then when the gas tank is fairly empty, the bow will be really light and the boat handle like a champ, and vice versa. Rule of thumb is, if the boat need weight up front, sand bags or relocate the battery up front so you keep static weight up there. Hydrostreams tend to favor all the weight you can get in the rear anyways but sometimes you need to get some up front too, and that is when you should use static weight, not weight that is always a variable.

As for your other questions, I have knee braces in my vulture and my tank does sit forward a little but not a lot and also, my bilge area is not covered by my gas tank. And you shouldnt cover it even if you dont have knees. But thats my opinion. These pics are from when I just got done doing everything and nothing is rigged or mounted. I'll dig up a newer picture later. Looks 20 times better now.

Thanks. The static weight explanation makes allot of sense.

The pictures are great. Interesting fuel tank. Mine is rectangular. 28" x 16" X 10"h.
It appears that the sump location on the V-King is not the same as the Vulture. The V-King's sump is about 6" forward of the transom and about 6"x6". The distance from the transom to the rear seat is less that 20". To get the fuel tank in front of the sump the rear seat would have to move 8" forward.
The tank would probably fit beside the sump, but that seems wrong.
Is the concern with covering the sump because of bilge pump maintenance or draining water from above the floor?
It looks like you would have to remove the tank to get to the bilge pump, right?
I see no reason not add some drainage holes through the floor to get water down to the hull.

How are other V-Kings set-up?

I would go take a look at Tonys VKing resto ( https://www.hydrostreamforums.com/viewtopic.php?f=13&t=3523 )and how he did it. The Vulture and Vking are pretty close. There is that hump in mine too so inside the bilge area, 1/4 of it isn't really usable. And yes, there are holes up front so water can drain all the way to the back. If I do need to access my bilge pump I will need to remove my gas tank but that is easy and I could have it out in 5 minutes. As for my gas tank, its not an original Hydrostream tank, which are square/rectangle. The prev owner put it in and a rear bench was built around it. and im going to do the same thing again eventually.

Here you cen see how the rear bench was when I got the boat. The lower portion of the tank is under the seat base where you sit.

Thanks again.
Tony's build is my reference for everything. He did such a great job on the build and the documention.
On Tony's, the fuel tank is notched to fit over the knee braces. I couldn't find a picture of his tank installed, but it appears that it would cover the sump. As you said, it only takes 5 minutes to remove the tank.
As for drainage holes, I meant through the floor.
I love how your rear seat is off the floor. It is probably more comfortable.

I am thinking that I will install knee braces. I will size them such the fuel tank will fit forward of the braces and not interfere with the rear seat. Fuel tank will cover the sump. I also want to eliminate the oil tank (switch to premix), and get rid of the hydraulic pack for the jack plate. I have a hydraulic pump that can be mounted outside the boat (on the jack plate for example).

Tony built his tank himself from scratch and put the notches in there. My floor will drain into my bilge hole as my tank sits off the floor about a 1/4 inch. Its winter and my boat is under a foot of snow but I'll see if I can find pictures somewhere on my phone. That rear seat in my picture is long gone. The wood was so rotten but that is how I am going to redo it when I make it this summer hopefully.

Yes, my tank completely covers my bilge. But I really have no reason to get in there on a day to day basis. I run the plug on the outside of the hull. My tank will take a bit more than 5min to pull, but less than an hour if I need to service the bulge pump for some reason. The tank also sits up an inch off the floor so any water flows right under it into the bilge. Mine is also completely one off that I built myself, it holds about 23 gallons. I'll add some pictures of my tank.

I returned the fuel tank to the back of the boat. I moved it about 2" to the right of the stock location so I could squeeze the battery in on the left side for better balance. The hydraulics for the jackplate are mounted to the right side outer stringer.
I also eliminated the oil injection system. The sub tank was going to take up too much room.
Of course the bilge pump failed after one week. Oh well, I'm still glad I moved the tank.