would lowering compression on a spoon or mugen engine be bad for it? like lowering it way down for boost

 

Not necessarily. Spoon generally does two kinds of builds: they can either rebuild your engine with stock internals, but balance and tune it into an endurance machine (which a lot of people like because a lot of racing classes require stock engine components) or they can go all out and do a full heart transplant, etc. They don't, however, build their engines for maximum performance; they build them so you can run them as you wish for a long-*** time. They balance the hell out of them, and leave your options open. 11.3:1 isn't really that high for a super-high performance Honda motor; you could easily run 12.5:1 on the exact same engine as long as you had internal clearance. Just the same, you can have them build you one and keep the CR below 10 in order to accomodate a turbo later. Hell, they'll probably even put the turbo on there and tune it for you if you ask nicely.