Really nice machining on those parts! Is that a Batmobile?

For your question on whether a 6090 would do, I can say that mine, which is pretty much representative of the generic 6090 class machines, would have no trouble at all. I can get around 175mm-180mm under my gantry, so the only limiting factor is the length of the cutter.

Obviously a longer cutter will give you deeper cuts, but tool deflection then becomes an issue, for foam this wouldn't be so much of an issue, but I could see it being a problem with MDF, as you'd need to increase the diameter of the cutter, as you increase the depth of cut, or the density of the material being machining. Spindle speed and feed rate also becomes critical as your "chatter" will increase. The longest cutter I've used is a 120mm ball nsoe, and haven't had any problems, although I did dial the speed and feed rate down a bit to reduce the chatter and deflection.

But in short, no you shouldn't have a problem at all just so long as you take the above issues into consideration.

cheers,
Ian