I definitely wouldn't use velcro.. that could cause static electricity and that's just asking for trouble.
I've used the brass hex shaped standoffs in my bartop, and actually, if you make the hole slightly smaller than the standoff, MDF will hold it fine. Once I got them in, I was considering some glue, but those damn things would NOT budge. Glue wouldn't hurt, but if you do it right, it won't be necessary... even with MDF. I mean, its not like the Ipac is going to be dancing around in there.