It really depends what kind of mod you're using. Just use your common sense in general. Has the F-15 cockpit model been altered in any way with 1.1..nope, So Im sure the Smooth cockpit mod would be fine to use.
Skins, runway mods, and others of this sort of thing should be fine, as again, no other aircraft models have been upgraded to make the skin not match. Explosion fps mods, Not sure, Mabey not, the fires seem to be rendered differently in 1.1. Brit's Su-30 mod, I think not.