Advice please, am looking to build up xc race steed, have found a nice Pace RC200 frame 18inch. I'm 6'1" 33/34 inside leg to small possibly? Usually ride 19inch P7 or 18inch Orange 5 no probs.

I'm 6'1" with a 34" inside leg – I ride the 19" – seems to be nice and comfy – although it's now fully rigid and my 'commuter' and the stem is back to the 110mm one –

And in it's commuter guise –

I'd guess you'd prolly be ok. I'm 6' 3" with a the same inside leg as you and have an 18 inch RC300 – which has same dimensions as RC200, but very slightly slacker angles IIRC. I've always found it a little cramped though – its ok but its a slightly compromised position. It certainly fits nowhere near as well as my more contemporary bikes like my Soul and Soda. Its just a bit short, but I sound a bit longer in the upper body than you.

Up until a few years ago I had a 19 inch RC200 too. Conversely I found that a bit too long – and it also felt huge and ungainly when I was riding it. Was certainly a more comfortable position for mile munching, but much less nimble. I prefer the 18 inch sizing, so I'd guess you definately would.

I seem to remember the effective toptube on the 18 inchers is around 590mm – I'd guess thats only a smidge shorter than your 5 or P7 so you should be fine.

I have a .bmp of the RC200 F8 Geometry…hang on –

TT length – 590mm on 18" and 605mm on 19"
71 degree head and 74 degree seat (on all sizes)
chainstay length – 426mm (on all sizes)
Head tube 'length' (height more like) – 125mm on 18" and 145mm on 19"
BB height is 306mm (on all sizes)
Standover height (by the looks of things (centre of top tube to ground) – 780mm on 18" and 810mm on 19"

I'm pretty much the same height as Richard and I have a 19", which is fine for me: I have a similar amount of seatpost showing as in Richard's shots above. I test-rode an 18" belonging to a friend before I got mine and it felt too small, so I'd hold out for a 19" if I were you. Then again, I have rel. long legs for my height (34-35 inside leg), so YMMV.