I've seen this written a few times, but I don't quite agree - the RAM showing as a disk is how they implemented the extra RAM on boards with a MMU. It shows like this when they aren't quite set up correctly. You needed virtual, set up in a very specific and careful way, with most boards, but sometimes there were other things to get right.The extra accelerator RAM can be used as a RAM disk but that's about it, so even if it did recognise it, its of limited use. If the system is able to see/use 4MB then you should be good to go as that's a good amount for an SE.
If you have a board doing this, drop me a message and I'll see if we can get it behaving.
The board in this thread... the logic board and card RAM are overlaid in the same address space it seems. There is no MMU. You should have 1MB on the logic board and 4MB on the card for best performance. You should be testing using System 6.0.7 or older, and need to try to get the ECC branded drivers working, to minimise unknowns.
Please leave the jumpers alone. This isn't plug and play USB. In the olden days, doing things wrong sometimes let the magic smoke out. You don't want to kill the card or SE. You have a board that makes your SE about 6x faster at the moment. Let's not create a card that makes the computer run at 0% of stock.