The general idea here is to have smooth, flat, ding-free surfaces over which to lay your fiberglass cloth. As far as fiberglass cloth goes, my basic guide to what weight to use is directly related to airplane size. For models with wingspans in the 80-inch range, you can use anything ...
[15] The new spar structure also allowed the wings to carry up to 2,000 lb (907 kg) of external stores. Also developed specifically for the Tempest by Hawker was a streamlined 45 gal (205 l) "drop tank" and carrier fairing; the redesigned wing incorporated the plumbing for these tanks...