(Chalky) Lines that rhyme should not be permitted as a combination, as I have pointed to someone out in Another Place. Makes it too easy. But other combinations might work.

The two posts must also not be allowed to share any letters.

[Rosie] Why not include lines that rhyme? Just makes it a different sort of challenge. In any case, you'd have to sometimes as lims are 5 lines long, so play would go 1+2 / 3+4 / 5+1 / 2+3 / 4+5.

[Rosie] Two lines that rhyme? An absolute necessity for some I'd say. That's why I suggested it. After all, aren't we supposed to be upping the quality?

again ... it will give those fly-in-and-fly-out-and-post-any-old-bollocks merchants [yup - that includes me!] a reason to stop and think.