These are durable enough when converted. A mid grad blade is a much better option than a heavy grade blade. I wouldn't guerilla duel, as it will most likely break the bladeholder.
The blade holder is plastic, and is the id is smaller than the TCSS blade. By sanding the end of a TCSS blade, or by very slightly honing out the bladeholder, you can get it to fit. I have a TCSS blade in mine right now, and I just sanded it down to fit. Takes about 45 minutes and some elbow grease. 80 grit at first, then move ot 180 for the final sanding.
Ultrablades are very bright and very even. The light grows slightly dimmer but the is no flare at the mirrored end.
TCSS blades are exceptionally cool IMO. they have a base flare, and they have a thin "core" that is reminiscent of OT sabers. The light is not as even, but it is a nice look. An MR boards will power A cyan lux III with no problem. you better order it soon, as they are discontinuing the Luxeon line in February.