I have just finished a RL20 Prostyler build, the pictures for which I've posted here in the Museum / members ride section.
I used a Redline fluted 22.2mm dia seatpost, and it took some tightening up.
I also have a Redline fluted 22.6mm dia seatpost, and this won't fit in the RL20 or an RL20ii I'm building now, without a bit of grease and a big push. The 22.2 will fit in both of course.
What was the correct size - a 22.2, which might result in a cracked seat mast tube keyhole, or a wedged in 22.6 that might never come out?