Originally Posted by academygaz

Pro 4 driveshafts fit, but you have to slot the outdrives longer to allow the bone pin to move further in when the suspension is compressed. You can do with with a Dremel/rotary-type tool. I took mine up to where the bearing holder is, thats with the ver2 spool.

I did it because I snapped a pair of HB alloy purple driveshafts, and I had just split down a Pro 4 for spares. Plus, they are a little thicker. I haven't tried HB steel ones yet, so I can't comment on them.