Cy – that's very interesting. By no means am I a seasoned cross (only done a handful of races), so I'm happy to accept that my technique is way off.
For me, it's the movement of getting my my arm through the frame in the first place – the top tube just tends to crash into my upper arm/shoulder, rather than being able to make a fluid movement of getting my arm through and the frame up. Like I say, it's quite likely my technique isn't up to much, but the frame is tiddly – as you know, 400mm c-t-c.
If the small sized >X< is, as you say, rather bigger than the small Soul on a c-t-c basis, then it should be fine.
If so, sign me up for the race version. I may be useless, but at least I'll do it in style..!
Tom