Here's a thought for you guys that run both outdoor asphalt and indoor carpet like I do...
When you buy your FK05, just swap the front diff from your FK to the FK05 and put the multidiff in the FK for asphalt. I prefer to have two different cars if I can afford it because I run the stiffer chassis and totally different spring/shock combo on the carpet car.
Speaking of which, I have an extra full BMI 350 FK chassis if anyone needs one. It's still NIP with upper, lower, shock towers, battery bars, and front upper bumper support all in satin black (by far the best looking color) that I'll sell for $165 shipped.