Hm. I may have to take a walk over to the ABCDTM forum and have a look-see.
I didn't have to stack or replace FET's for the FF/FK180's. the HPI stock and HPI modified 45t both fit in without any major headaches at all, seeing that the F?180's drop in without any modifications. In all honesty, the FF180 (stock in a Micro) even at 6v will make for an Xmod that's nearly twice as fast as a stage 2. I tested one of mine (full stock weight with a 5th cell) over 30 feet to make the voyage in 4.21 seconds with a run that was definitely less than straight on low-pile industrial carpet, so I would venture to say 30 feet in 4 seconds flat easily which equates to about 17mph in about half of maximum range. An RS stage 2 Xmod wont hit 17mph over any distance and any amount of time. With an 11t (which the aforementioned test was run with) it would top out in the mid 20mph's at only 7.5v and stock weight.
I've been discussing the 180 family in an Xmod on another Xmod messageboard for about 2 months now and it's since become the unquestionable motor of choice, so I can pretty much give information in an almost archival state if needed. With it installed, it looks like this:
And this:
If you have any questions you can IM me at DeepBlue963.