Without some fast RAM WHDload will not work, not even a single game .slave that I know uses only chip RAM.
Just not true. Lots of slaves work with only 1MB or 2MB of ChipRAM. (Preload often wont work, but the game will run without it)
How do you think the CD32 WHDload CD's work? They do not have any fast RAM.
Or on A600's? The majority of those also have no fast RAM.
I had some problems with KS3.1 in A500, but there is a solution on EAB forum. You might need to put some missing resistor packs near CPU slot.
Oh yeah and I forgot to mention, depending on which A500 motherboard you have you cannot use a 512Kbyte Kickstart ROM (like KS3.1) without some soldering and rewiring of ROM pins.