good on ya dgleue for tracking that down! i knew one of the RB bikes had a small seat post andi think the mb-4 frin 1991 had one but i sure didn't think any of the xo's had one and somewhere i have a 1993 catalogue. duh!
I just found my catalogues and in the 1993 catalogue there is nothing indicating seat post size other than it is a kalloy #242 which likely came in many sizes. However the interesting thing is that in the 1994 catalogue th XO-4 is 26.2, so is the XO-5 and the CB-1. as well the MB-4 had a 26.6 post along with a number of other models. Maybe yours is a 1994.

some more info to go along with the above. the 1994 26.2 post was a Kalloy #200. this is a straight post ie; there is no clamp. also check the headset in 1994 it was a YST 8002G. dglue ,if you are interested email me and i will give you the specs for both years 93/94.