There have been threads lately dealing with use of HO roadbed or N roadbed for HOn3 track. Likewise, on the general forums there is currently a discussion underway about cork road bed shortages, specifically in HO.
The following URL offers roadbed specifically for HOn3 use with either 45 degree, 60 degree or square cut!
http://www.homabed.com/site/890800/page/494803
The roadbed is made out of homasote. At one time back in the 70's and 80's this was the sub roadbed of choice in model railroading. I have always preferred homasote as the base table material for my 2 foot wide shelf layout that runs 60 feet around my attic. It looks like I might start using this special road bed as well. Homasote on homasote!
Richard
If I can't fix it, I can fix it so it can't be fixed