Sealing decals on Alclad finishes

Future will leave a glossy coat if that's what you're looking for.

I usually seal in my decals with flat clearcoat, not Future. Besides, I used to hang them on the ceiling but never again. It became such a hassle dusting them off plus you risk breaking off delicate pieces, like propellers, machine gun barrels, antennas, etc... From now on, I'll display my kits in glass display case or a used curio of sort. 

To clean dust from ceiling or shelf bound models, I simply hold them under the shower and let them drip dry after.  The delicate parts never get broken that way.

Any sealer you apply will change the tone of alclad.  You can brush on some clear coat on the decal only.  A laquer flat clear will leave no brush marks.