Don't worry about it. TMX 100 needs very little reciprocity compensation for those exposure times. Depending on who you talk to, you don't need to compensate at all for 2 seconds, and even at 4 seconds you're not going to lose much. If I recall correctly, in Howard Bond's tests he found for his purposes he needed only an extra half second for a metered time of 4 seconds with TMax 100.