I have a pair of SCM-19 v2 and use high quality jumpers that match my speaker cables. I found both clarity and smoothness improved with jumpers instead of the stock plates.
I asked the owner of Audiosensiblity cables about diagonally connecting speaker cables as you described and he suggested it is better to connect the speaker cables to the base driver posts since it uses/needs the most juice. He also recommended using one set of the best quality possible speaker cables along with jumpers rather than bi-wiring with two sets of lesser quality speaker cable (for a given budget.) I presume the same logic applies to tri-wiring (unless you are using multiple amps?)
I recently replaced the stock binding posts on the ATC's with WTB Nextgen, which required enlarging the mounting plate hole diameter. It was a bit of a project but here again clarity and smoothness improved.
FWIW jumpers seem stupid expensive for what they are and I would suggest making your own with appropriately high quality speaker cable and terminations, i.e. 4 banana-spade jumpers for each speaker.