Filling in instrument holes

[BellBoyBob]

I am going to have to re-arrange my instruments on my fiberglass helm box. Since I have GPS, I may do away with the analogue speedometer and I want to see if I can flush mount the GPS into the box and add fuel guages. The box thickness is about 1/4" where it is just glass. On the face of the box, there is a 1/2" plywood doubler to support the steering wheel. Where I need to fill the holes where I cut through both glass and plywood, I would simply fill the hole back in with plywood discs, the add fiberglass with micro balloons, sand. fill, prime and re-paint. Where I have no plywood doubling, what could I fill the 1/4" depth on with? Would you use a fiberglass mesh of some sort?
Thanks,
Bob

[Helmar]

I would epoxy the plugs in and then glass in some patches to fit the hole.
Evercoat makes a Kitty hair mix as well which is very sandable.

Looking forward to what others come up with too.

[Tim_Mattson]

Bob,
When faced with tough to reach areas needing a backing,I`ve globbed up some epoxy or Duraglass on a small scrap of Dooskin material just larger than the patch.A pc of glass mesh can be wetted out first,then coated after grinding away the wood or leave it and forget it if not visible.
A pc of cardboard can work too,or even painters tape.A screw can be sunk in until it pins it in place or prop a stick or board to hold in place while setting.
Concave the hole slightly and the plugs won`t pop out.
I`ve also used scrap pcs of hull to bore out plugs to fill the gap with glass,sometimes even matching the hull.
TimM