Boat looks great, Yaha will easily get him on plane, provide plenty experience until next power upgrade. My son, Hydroid Jr, had 8' Tiny Titan hydro w 5hp tiller at 7, it's been a slippery slope to his 22yrs now, can drive pretty much anything, racing hydroplane(65mp), Voodoo & Critchfield w 56ci OMC. Good for you for supporting your son's boating interest/passion, having him plan & assemble his ride with your guidance, take ownership/responsibility.

Based on our own experience with new era center steer VDoo, my quick suggestion & for others to offer opinions: move fuel cell back under rear deck for several reasons.
Namely: to keep it out of direct sunlight/heat/vaporizing gas, open cockpit access behind seat to step into boat & tripping hazard, move weight rearward(although consumable) to reduce wetted surface, option to place another bucket behind driver so he can take friends/passengers out for a spin.
However with fuel fill hole mid cell you're limited how far back you can push it & still fill effectively unless you run a fill neck hose/screw cap up through rear deck.
Give some thought if you haven't screwed it down yet.

Looks killer Mark!

"I didnt know where to place it so I probably should have asked around. I can move it back a little bit but not alot due to the battery, the dog legs etc."

If you can, use an ATV(~8lb) battery rather than full Large(~30lb), place/afix it on the outside of either knee brace so you can push fuel cell back. The small 8lb battery offset from centerline will not create significant imbalance.

On almost any planing hull you can just assume that the center of gravity and buoyancy is 60 to 65 percent aft of the bow.
https://www.boatingmag.com/how-to/balan ... ight-board

That's coming along real nice! There's going to be some jealous kids around lol