Slitherine

If a BG has a number of bases that doesn't divide into its frontage (and thus has to have an incomplete back rank), can there be a gap in the back rank?

That is, if I want to provide rear support to two BGs with a gap between them would the following be legal?
= base
= gap

Yes. There is nothing in the rules to prohibit it.

Depending on the number of bases in BG doing the supporting IIRC it has to be at least half the amount of the supported Bg.