Hello there Dan.
Loads of horror stories of the 951 FRO snapping (FRO was lighter as it had a monocoque frame) as far as I'm aware it was limited tot he FRO and they stopped producing it in 2012?
I had a 951 FRO in small. Super light build, think about 36lbs all built up and I never snapped it. Did various UK uplift days inc inners and Ft Bill, 2 summers in France and the mega.
I'm not a big tanker and generally pick lines as apposed to plouging through and try not to huck to flat.
Last summer I moved onto a medium Wilson, it's not that much bigger than the small 951 and I felt a lot more comfortable and confident on it and my strava times reflected this. I'm about 5.6 or 5.7.
What 951 are you looking at?
Here is my old one.

If you don't end up buying a 951, I'd go with a 2011 Wilson. Mine is for sale ;-)