I recorded a 6 CD set on an 80 min MD in 66k and it sounds pretty good. Of course, when I get some Hi-MDs, I'm gonna record in Hi-SP to get the best quality but for now 66k is fine.
I installed Sonicstage 3.2, so now I have my answer. I was very happy to find out that I can finally edit and erase tracks on my MD recorder that were recorded with Sonicstage.
I'm still trying to work out why SONY say everywhere (on sites in the manuals) that you can put put 10 hrs or 13 hrs of music on a standard 80 min MD in Hi-MD mode, when it seems that there's no way to do it. Can someone help me out with this?