OK, currently, routers2 does not support Option[]:dorelpercent.
However, I think it will be relatively easy to add this functionality (since it is just a slightly different case of the existing aspercent option) and I'm in the process of adding it. If you'd like a copy of 2.15beta7 to test once Ive done this then I'll happily send it to you -- I'd like to be sure it works as you expect before I leave it. I'm feeling happy and accommodating because I've just been sent a couple more DVDs
V2.15 should be released about Christmas, provided all these bits are OK.