I'm a "FELON"... I 'free'ride my 100m-forked XC bike on trails I find, I love going uphill as well as downhill, I tackle jumps I know I can handle and not cause my wheels to explode, I don't use my bike as a bashguard, I use my XC bike for DJing, but there's so little (about 2 hours per 3 months) that if the frame failed it won't look obvious.
But team-It sticking a fork if too much travel for the frame is something I will never risk, not only is it obvious to warranty-people and mess with the geometry and handling but mainly because you stress the frame
everytime you ride the bike. Whether it be tackling a new line or a casual commute, the frame will be stressed overtime everytime. For me the frame get stressed when I miss a jump or drop, but for your case every ride.
If only every manufacturer does what Orange does, state clearly on their website: intended use and fork travel limit.
Here's an example for their E8 XC bike, and their website also provides above-average detail on their bikes, which is a nice and reassuring thing.
Here's how the above pic reads:
Orange E8:
- Fork travel between 63mm (eg. SID) and 100mm.
- Not suitable for: DH, FR, BSX, 4X and DJ.
- Suitable for: Trail riding, XC racing and "Adventure".
- Acceptable for: Touring.
Too bad your Xtc isn't steel, they're more forgiving but not so forgiving that allows you to mount a double crown 190mm DH fork on a 63mm XC race frame. And also I'm not warranting exceeding travel limits at all.
I ride down stairs on my XC bike, no probs, just stay calm and roll down. Easy-peasy. 100mm is more than enough, unless you a pvssy or a fat-arse.