For future reference (for folks reading this far), Ergo kits in KAT can use either R2 or R1 for the bottom row. It's just important that the 1u keys in the thumb clusters be R2.
With R1, the bottom row gets a slightly more optimal sculpt.
With R2, the keys in the bottom row are interchangeable with those in the thumb clusters.
Note that if you go with R2 bottom row, double-check that you've included 2x R1 1u caps of some sort (for Ergodoxian boards that use 1u keys in the central columns).
Regardless of what you choose, the convex keys you supply with the kit will be technically R1, but their actual shape looks fine alongside either R1 or R2.