Well, I've just spent the last 6 hours upgrading my MK2a from 16MB to 32MB. This must be the least productive hardware upgrade i've ever undertaken!
Now, I've been soldering things since the age of about 10 (I am currently 28), including some rather bizare mods involving surface mount components on NetStations (don't worry, probably only means something to Hugo, and even then not much), so I wouldn't consider myself a amateaur.
All I can say is that is is way more difficult than, say, replacing the surface mounted StrongArm chip.
The things that, IMO, make this hack difficult are:
a) that the legs on the memory chip are very fragile and very small and very hard to straighten. Even then, they are only just long enough and you have to get them all at exactly the right angle, which is just shy of 90 degrees
b) you definately need a high-strength freestanding magnifying glass. My eyesight is very good yet there is no way I would have been able to complete the work without a glass (I did try, before giving in).
c) The solder prefers to bridge adjacent pins than join the two chips if there is even the tinest gap between the bottom of the pins on the top chip and the top of the pins on the bottom chip. I would very strongly recommend the use of a no-clean flux pen. Maplin (code HH62) and RS sell them.
It would certianly be useful to have all the info in one place (took me an age to find everything I needed on the bbs) - I might look to start doing just that over the weekend if I get a chance, then ask Tony to update the FAQ.
I won't be doing another one of these in a hurry, and definately won't be trying for 48MB or 64MB using this method. Howerver, no broken pins and I do get:
Thanks to mlord, pgrzelak, Hugo, Stu and everyone else who helped to make this possible.