Screw it; I'll take the risk. I'm assuming a floor is 3 meters (10 feet), so I'll need 6 successes. On a glitch I need a single success on a Reaction + Strength to hold my grip; critical glitches aren't mentioned.
So, approaching north west corner to avoid the doorway as much as possible; each test is a complex action, and assuming average initiative rolls I'll have 3 complex actions per turn.
Gymnastics 1 + Strength 4 + Assisted Climbing 2 - Surface 4 [Physical 8]:
3d6t5 2 [6, 2, 5]
Gymnastics 1 + Strength 4 + Assisted Climbing 2 - Surface 4 [Physical 8]:
3d6t5 0 [1, 1, 2]
Hah, critical glitch. I'm below the threshold for taking falling damage, though, soo, you'll have to let me know how you want to handle this one.
Reaction 7 + Strength 4:
11d6t5 3 [4, 4, 6, 4, 2, 1, 1, 2, 1, 6, 6]
More than enough to hold on.
Assuming I can continue climbing, I need 4 more hits.
Gymnastics 1 + Strength 4 + Assisted Climbing 2 - Surface 4 [Physical 8]:
3d6t5 2 [5, 1, 6]
Gymnastics 1 + Strength 4 + Assisted Climbing 2 - Surface 4 [Physical 8]:
3d6t5 0 [1, 1, 4]
And another critical glitch... This was clearly not meant to be!
Reaction 7 + Strength 4:
11d6t5 3 [5, 6, 1, 4, 4, 1, 2, 4, 3, 1, 5]
Enough to hold on again, even if you were to take away 2 or more dice for a critical glitch.
Again assuming I can actually continue.
Gymnastics 1 + Strength 4 + Assisted Climbing 2 - Surface 4 [Physical 8]:
3d6t5 3 [5, 6, 5]
And success!
Well, let's see what the GM makes of the critical glitches. Interestingly, only glitches are mentioned in the Climbing section, and both of my fall checks had enough successes even with massive negative penalties (at least 1 success with only 3 of 11 dice on both tests). And with Traceless Walk (which I assume extends to climbing) even hearing me scrabbling around out there might be challenging. Worst comes to worst, I'll just leg it, unless Robin somehow sees me and manages to catch me in the air as I didn't see his post until just now when I had already made my rolls. Levitation, doh!

I'll leave posting the results until we know what happens. Man did I never think a single die would make that much of a difference...