Here's the thread on leg amputation ...
http://www.picaxeforum.co.uk/showthread.php?t=13811
And a 'more sensible' suggestion for using SMD on a carrier to fit a smaller DIL footprint ...
http://www.picaxeforum.co.uk/showthread.php?t=16154
Looking at the pin-outs; if you wanted to go the leg removal route it seems you have a couple of options, three when the 14M2 is released. All with the caveat that none have been tried.
The 14M2 would be ideal with the bottom two pairs of legs cut off.
The 18M2 could have the top pair and lower three pair removed, and if that hit the silicon die, top two and lower two pairs but you lose the re-programming ability after that. Actually the 18M2 could be reprogrammable if download Serial In were paralleled to another 18M2 but with the risk previously discussed that you wouldn't know if the decapitated 18M2 had been successfully programmed. For a one-off that may be acceptable.
Another option for the 14M2 would be to remove the upper and lower pairs. That would lose the 0V/+V pins, but could perhaps be mitigated by using parasitic power through input pins. I'd opt for taking the bottom pair off.
I'm not sure what the actual silicon die size is nor where it's placed in the package. It may actually be possible to be more brutal.