When filling holes on a boat, it is usually between let say... 1/8 to what, 3/8 maybe?

i have a
thru hull bottom water pick up to fill in
not a thru transom water pick up

so, the hole is like 2 inches deep or so...
i would guess there is somekind of coring in there to reach that thickness, unless it is solid glass but i would be surprised...

what would be you way of doing it? I was thinking to fill it with structural fiberglass putty, and finish with 3 layers of 1708, inside and outside, then finish nice and smooth...
any other suggestions?

Mmm...
not as many fb glass guys here like it used to!