I do have a question,
I will be replacing my supra 512 card with an "expansion systems" Baseboard ram upgrade, that is a two part memory upgrade:
one part sits on the Gary IC socket, and the Gary plugs into it, piggy pack.
and there is a small ribbon cable to goes to the memory board that can hold
up to 4 megs of RAM giving a total of 4.5 megs....
will that memory expansion still work with the line cut going to the trap door ram?
is anyone familiar with upgrading the Agnus, and using the Baseboard ram upgrade? 
I just did this.
The ICD Baseboard will not autoconfig more than 1MB chip of ram on machine with ECS agnus (512 motherboard and 512 baseboard). The extra RAM must be configured with the adram program on the floppy disk.
With baseboard you need to add the ECS Agnus, Add a wire from the P4B gary daughter board to JP2-2 (second pad on the JP2) and make sure no other connections are present on JP2. Then you have to cut the JP7A (on rev 6a A500) jumper or the equivalent line on the rev 5 machines. Now you will have 1 meg chip with ICD Baseboard. ICD had a GAL upgrade that allowed autoconfig of fast ram but I dont know where to get it. I use to have it on my A500 that got tossed when I went to school by my parents... darn it..
I have still yet to find the DOCS for the ICD baseboards but I just did this mod with a 6A mb and remember some of the details from the docs over 15 years ago!
Another thing.. you want super denise but dont have or can't find one... Indivision ECS will support ECS screenmodes with normal denise over the VGA port AND the cool Graffiti modes!!! Best mod evar!!
I am in the middle of finishing up a REV 6a A500 with all these mods...
Tim