64MP hawkeye sensor over ethernet cable extension

I’m using a RaspberryPi 4B + arducam ethernet cable extension UC891/UC892 and a 64MP Hawkeye camera module.

I’m having some trouble getting it to run over an ethernet cable > 8-10ft. (In theory it claims up to 15-20m has been tested… I’ve also tried 30ft and 50ft cables with no luck).

AFAIK the cable driver IC’s THCV241A/242 are capable of up to 1.2Gbps per MIPI lane, and up to 4Gbps per LAn cable pair. I’m certain that I’m not going to get the full distance at full speed, but I’m trying to figure out how I can slow down the link to something more sustainable.

I’ve cut the camera mode down to 3840x2160 , but still fails the same. I’m using an ROI that captures about 1920x1080 out of that frame and this is where I’m not sure how things get setup. I expected that the ROI would cut the data sent over the link, and thus the clock could be reduced. I haven’t seen any evidence that the distance increased by reducing that ROI / video mode, so it seems that the MIPI/V by 1 link is still at the same speed, probably set by a driver / on board uC /flash?

I have a few questions then
#1/ How is the MIPI/ethernet extension link speed setup and can it be modified ? (easily?)
#2/ how far have been people able to run the ethernet cable with a 64MP Hawkeye sensor?

FWIW, I’m using cat 8 class ethernet cable - which should be able of sending 40gbps (over 4 pairs) over a 50ft cable… (if I believe the mfr specs…) 10gbps per pair should be more than 2x the bw max of the thcv chipsets - so I expected to be able to pull off 10-15meters.

I do notice the cable drives get pretty toasty - I don’t know if they’ve been programmed to be more moderate in drive strength to manage power, or if they can be boosted.
I do have the THCV register set - but since these are meant to be plug and play - I would guess that they’re being controlled by the on board uC and/or flash settings, may not be readily accessible via the RPI I2C bus - and then I might be fighting the on board control.