Sit it in slightly sideways, I ran mine for a year like it and it was fine (Matteh and most others still do)...
Last winter I modified mine...doesnt need to be done but im glad it sits properly with the standard rubbers on now too...
Hopefully that will give you a bit of an idea...
I could have taken more out but I wanted to retain the hole on that side of the subframe for my engine mount rubber to sit in, so I just took as much as I could off