I think so mate, the 1000's might be a tight fit, but the shorty 750's and 2000's are definitely no issue. I may even be able to get 1000's in the same shorter 1/2 length.
The SR20 rail kit I sell comes with a plenum spacer to help the 1000's clear the upper plenum. Perhaps you could do a similar thing to the RB plenum halves using bakelite or a similar insulating material, that way you would stop the heat transfer into the upper plenum also.
I am using twin Proflow stainless mesh filters, I haven't cleaned them in 3-4 years, since they were installed. I can't remember what micron they were...
The paper filters I have been buying were SX brand, suitable for alcohol fuels. (They have a similar 8an housing to the proflow/Speedflow style filters, and might just drop in to them.) I run the SX fuel reg in my car without issues so I knew it was good gear.