The R0642 can be used with the "stacks", I've done it a bunch of times. Just warm the filter, lube it up with some silicone spray and it'll slide up over the unmodifed stack. When it's time to clean them, I don't remove the filter from the stack, I simply unscrew the stack from the carb.
I find the MG2640 filter to be a bit of a PITA to get on and back off for cleaning, even if I warm and lube it.
On my Convert, I used the original "stacks" and the RU2450 K&Ns. Fit nicely and are relatively easy to remove for cleaning.