Your problem may be related to several factors:
Both Tamiya acrylics and Future require longer curing times, especially when overcoating with a different material. I'd suggest a force cure for this application.
Tamiya glosses (and semigloss) have a gloss enhancing additive that inhibits bond of overlying paint. This may be a factor here.
Future is supposed to be a good primer for Alclad, but Tamiya paint may not be. The solvent system in Alclad is extremely aggressive, and may alter the properties of the underlying, fully cured coating. It is not uncommon for such an effect to cause swelling of the cured coating.
I've heard of three coatings that have been used successfully under Alclad: Alclad primer, Krylon Gloss Black, and Future. From what I have seen and know of the coating system, I would not put anything else under Alclad.