Amiga 500 ram?

[AmiDude]

I don't know what you mean by "trap door memory hack", because personally I won't consider this;

http://amiga.resource.cx/exp/a504plus

as a hack. I actually happen to own one of these, and it worked straight away as 2Mb Chip RAM expansion. No other mods required, because A500Plus has 2Mb Agnus from factory. Good luck finding one.

I've had an A504plus in my A500+ and it gives 4MB Fast RAM memory.
See link:
http://www.amiga-hardware.com/showhardware.cgi?HARDID=929