Thanks for the help everyone. I have not tried to tackle this again yet, but I did contact Hobie directly and got this reply:
Try drilling a hole in the broken off screw with a 3/16” reverse drill bit and it may come out in the drilling process. If it doesn’t try an extractor again once you have the hole drilled. If you end up destroying the ¼-20 threads, there is enough room to tap it out to 5/16-18 and go with a bigger set screw. The V-frame would need to be drilled out to 5/16 in that case.
So, they can provide a 5/16-18 bolt if we need to go that far. Kayaking Bob gave some advice using a dremel saw blade to attempt to get the broken bolt out again, but I'm not going top lie when I say I didn't follow him completely, but luckily my friend Travis did and he will be helping me... he's a bit better with this kind of stuff but I'm learning all the time. I'll let you know how it turns out, we'll work on it tomorrow night. I think the caution everyone gives about fluids and going slow is very wise, so will be doing that!
And, I think from the contact I had with Hobie that they would probably process this for warranty (or help me with hull replacement per their typical policy). I'm hoping to save this one though, as it's not a crack in the hull (I've had a couple of those) and it's been a good AI