Mount the battery pack back further.
If the wires arn't long enough, use the servo extension.
If you don't have and extra once, splice and soilder.
or re locate the RX.

It's a simple fix to make a hatch
if you have the tools already..iron, scrap wood, scrap covering.

If you decide to just add weight to the rear and place it on the stab, becareful when you cut the film.
If you score the wood slightly , it 'll weaken the wood plenty.

Me..If i had to add weight to the tail...I would just take a drimel to the reaest bay of the fuselage
and expoy the wieght on the inside. Then just cover it back .

But I'd probably move the servos back first if i had to.

Then I'd probably add those light weight non aluminum landing gears and make it a tail drager first..just to keep the .46 TH on it.
Becuase I would probably slap a 12oz tank in it too

You can always get bigger piaon wires...but nah.