Apparently the Radar Cross Section of the Panavia Tornado has never been published, if the talking heads on-line can be believed. They may be correct, as I can't find that info. The F-4 RCS I found indicates 6-10 m2, which to me seems almost optimistic for that collection of lumps and bumps!

Ultimately, this isn't important for my cunning plan, I could go with either one, just seeing if the hive-mind can get me any better answers.