Personally i think if he has bought a 10 then i would put it in a .65cuft enclosure, if he wanted lower beats he should of bought a 12". I would never put a 10" type R in a 1cuft box unless a customer specifically asked for it. (and Id advise against it)
If you got a 10" free of something and had to use it but wanted it to hit lower like a 12 then maybe Id use a 1 cuft box but on most occasions if you want it to hit low just buy a 12.
Alpine spend a lot of money designing and testing subs, why would they recommend a 0.65 cuft box if it sounded good in 1 cuft?
So summing up, Pete id recommend you use the Alpine recommendation for the box size and get a 0.65 cuft box
Just my opinion!!!