I have just seen that this will be my 500th post. Recently I realized that I enjoy a lot reading the posts of some persons I follow daily - and that if they can do it daily, why shouldn't I? So I have started to do it much more frequently that I used to.
Among calculator lovers, like among many other amateur disciplines, there are two "schools" or way of thinking. On one side, you have the purists: those that want the original calculator, as close as it initially was- with their pluses and minuses. These would buy a tall keys HP41c and leave it like that.
On another hand, you have the performance seekers. Conscious that time has gone by, but still loving their calculator, they do not have a problem "upgrading" it to a better performance level. It is to these that the offerings of Systemyde, Teenix and Panamatik are aimed to (respectively aimed to the HP41, HP67 and HP25 calculators).
However, for the HP41C you can do upgrades "on the cheap". For all Full-nut calculators, the processor can be replaced easily and the host calculator becomes truly the "donor calculator" !! If you put a CV circuit in a C calculator, you will have a CV in a C body (which I vastly prefer, color-wise, to the CV or CX). Same as using a CX procesor, but these are much more difficult to find, since not too many full-nut CX were made.
At The Calculator Store we always have some tested, dependable CV circuits available, and, from time to time, we find a CX. However, these are few and far between. However, when you put a CV circuit, you get up to 319 memory registers instead of the 64 original, and keep all 4 slots available!