Post binding for crude tone control

bojack---do you know this from personal experimentation?  Perhaps that hot top end is only a matter of synergy and yes, changing cables, plugs, & outlets can solve this issue.  I have gone through this with an overly bright midrange on a pair of large DIY speakers I bought some years ago akin to Legacy Focus using Eton drivers.  I thought gold would smooth out the mids but actually, it seemed to exacerbate the problem.  Tubes in the source did help some using either a Raysonic 228 or a Modwright Oppo BDP83 SE but what really did the trick was much better cabling and getting all the gold out of my system.  My wires are mostly DIY silver plated solid core copper.  I went exclusively to Oyaide 004 and 046 plugs and my outlets are all Cruze Audio Maestros and there is significantly more detail but the mids aren't as pushed forward and sound more natural  without the bite.  There is no reason the OP couldn't achieve the same results with his hot top end doing nothing more than improving the jumpers or tri-wiring.  Along those same lines, I've found the IeGO 8095 rhodium over PURE silver plug to be both very detailed and extended and yet somehow able to smooth out an aggressive top end and brightness in the midrange.  So bojack, nothing personal but I'll have to disagree with you on this one

I have SCM40’s too that replaced SCM 35’s. I have biwired them, using the stock jumpers. I had originally tried fancy jumpers from Cardas, but the sound was smoothed too much. I was surprised that I preferred the stock jumper plates.

These speakers benefit from biwiring, in my opinion. My SCM40’s are not bright or hard at all. The SCM35’s could be bright and hard on poorly recorded material.

Binding cables to one of the bass driver's posts, and to one of the tweeter's posts - I wonder if this really works, or ever observable, but good idea nevertheless - to try. Thanks.

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.