it depends on model itself and what i'm in the mood for. i generally just cut through the covering and epoxy
the wieght to the rear former. At the flying field for a quick job. I use CA or 5 mins expoxy.
If i built a model previousely and knows it's going to be nose heavy. then I don't
mind beefing up the rear section of the fuselege. The 4* 40 is a go example. The weak piont of the fuselage is
behind the former of the wing mount. i also paint the canopy black and screw on the canopy. The cokpit becomes
the battery's mounting bay. It allows me to move the battey pack farther. Nothing fancy, tie straps to secure it.

For tail heavy model, sometime the battery pack has to go into fuel tank area.

I build in hatches to most of my models anyways. it's alot easier to remove the fuel tank at the flying fly,
if the clunk line gets sholved forward and get stuck, then to be shacking the heck out of my model.lol