@Kai
Good start to EAB life- I like your project and contribution.
We also recently made a low cost trapdoor expansion for the Amiga 500 Plus here which upgrades to maximum 2MB Chip:
http://amigakit.amiga.store/product_...roducts_id=502
We also have the A500 512KB expansion based on the same board:
http://amigakit.amiga.store/product_...roducts_id=767
Our aim was to make a very low cost memory expansion that is readily available to keep our hobby going. We were concerned with quality/price issues of products from Ebay sellers and part time "resellers" in the Amiga world.