Remember if you send somebody on a Qualifying Cross Country that counts as only one solo sign off.
However if you read LASORS closely if you send a student on a non qualifying cross country flight where the student lands at another airfield, each of the flights counts as one sign off.
I think Training Comm 1/2007 gave some guidance as to supervision requirements. It wasn't too specific but gave some guidance none the less.
If in doubt don't get out. I twice decided as an FI(R) not to send two different students on their second solo's.
When it comes to QXC's you really have got to be sure on the weather. Check all available sources, Met Form 215, METARs, TAF's for the airfields they are going to and surrounding ones.