Ah, Leelee, it looks as if you need the ISCG bolts to hold the mount against the frame and the cutout for the BB cups will be larger on the drive side. Easy to do with slots like you show. I'll change the ESC side mount to kink downward, lots of bikes have a pivot on that side near the BB so others may need the same design also.
My preference is a spring loaded tensioner, it seems to make life easy when it's working correctly. Constant tension, easy chain removal, allows for one-piece engine mounts. Hate that I have to make it custom and there are random issues until the stupid thing is 100%. FastJohnny is right about some flex- without a spring in the mix, we can lose a bit of tension under full throttle (when we particularly don't want things to fall off) and there can be some wobble in the BB/spider/threaded FW. I'll keep fighting the spring tensioner design for these reasons while keeping an eye out for better ideas
This is basically the smallest opening that will fit the Talon ESC.
Also, this BB from Lunacycle (https://lunacycle.com/isis-bottom-brack ... r-cyclone/
) can be adjusted to fit BB widths 68-95mm. Leelee, the outside face-face width of your BB with the BSA adapters is 96mm, right? Add 4-5mm for the thickness of both Tangent plates and then we'd be at about 100mm. This guy from Luna fits 100+mm wide spacing (https://lunacycle.com/isis-bottom-brack ... r-cyclone/
). I'm setting the chainline for the kits based around these two BB's, with 31mm of spindle stickout on the drive side (end of spindle to BB face). If we use the same spider/FW arrangement, the chainline is repeatable.