So I ordered both sizes. Perhaps against intuition, the BZ100 are the larger size. I haven't got my Astrotec AX-35 yet and I didn't heat or shape the molds but I tried snapping in the IEMs I do have handy: HiSound Audio WooDuo 2: Loose fit inside the BZ200 Nuforce NE-600X: Tight fit inside the BZ100 Monoprice 8320: No fit inside either Looks like I'll have use for both sizes after all, assuming the molding process goes well and I like the result, that is. From pictures I'd also guess that the Astrotec will fit one of them, most likely the BZ100 better than the BZ200 but I can't tell for sure before I have them.

Well I wasted 20$ for nothing, couldn't get a proper seal and tried to reheat the mold two times. Eventually it just fell out of the earphone slip and I couldn't get it back to being molded properly. First pair I messed up by heating both at the same time, in which i forgot what went to what ear and they had bonded together. Guess I gambled and lost.

Just recieved the BZ200's that I ordered, super fast shipping. Unfortunately they don't work with my headphones (M6-BK http://www.amazon.com/MEElectronics-Sport-Fi-Noise-Isolating-In-Ear-Headphones/dp/B0038W0K2K) so now I've got 2 pairs that I can't actually use with any of my headphones..