Hi Dave,
You can find info regarding how to install modules into an HP-41, on some PPC Journals. I'd like to be more precise but it's too much time since I placed my Quad Memory into my 41C guts... ;-)
Anyhow, I remember I only made some thin wire soldering and place the Quad board inside a narrow space beside the battery compartment. Some others with more recent experience will sure be of much better help.
Regarding the Clonix part of your message:
I'm not planning to sell bare Clonix boards as I'll have no way to test its functionality. Anyhow, I can't see a feasible way to implement the said BootLoader's needed hardware (please take a look at Clonix hardware info to make yourself a picture: 24 x 13 mm PCB...less than half square inch!), furthermore, if such Bootloader is implemented (on an oversized board, inside the HP-41 guts), an external connector shall be needed to face the re-programming tasks.
Which kind of connector pair (male-female) would be used??
There are really very few 41'ers ready to open, solder, drilling... into their loved 41's... not a general solution indeed. I think Clonix is intended to serve as a solution to as much users as possible, keeping the module shape, the calc shape, without intrusive surgery, with a cheap and easy to find programmer.
Oh! I almost forget a small point... Should the Bootloader portion of the PIC code becomes corrupted (whatever the cause)... there will be no way to recover the module (or the calc provided you built the Clonix inside it) but re-openeing it and re-programming it again in the same (traditional) way Clonix is already doing...
Any good idea (with drawings, PCB's layout and fully documented, will be greatly appreciated not only for me, but for the whole 41'ers community...;-))
Please don't misundertood me, Bootloaders are an amazing possibility of an amazing device, namely, the PIC's microcontrollers, but there are many reasons, to my eyes, for which this particular feature is innapropriate in this particular case.
Diego.
P.S. On the contrary of what has been published in other PIC related forums, I have never seen a single 18F252 PIC with Factory pre-loaded Boot-Loader, all of them come programmed to all zero's. (Erased state is all one's).