I know you have gotten a lot of answers so far on the MoHPC forum, but it would be good to contact the makers of the modules at their own websites and let them know this new forum is here and ask them to post their own answers here. I would like to see a lot of the 41 conversation come here as I believe the 41 meets a need that the other calculators cannot. It is the only HPIL enabled calculator ever. (I have a couple of 71's too, but the 71 is a hand-held computer which, although far more powerful than the 41, is not as practical for calculator use, IMO. I really like the 71 a lot, but not for the same applications I use the 41 for. I have a 75 also, but it is even too big to be called a hand-held computer.) I'm not very interested in most of the things the MoHPC forum talks about, so I was glad to find this one that is more focused.
Clonix:
http://www.clonix41.org/MLDL2000:
http://www.kuiprs.nl/hp41.htm