You may be out of luck there. IIRC the switch stacking links don't even run in normal 'Ethernet' mode, they use something called HiGig and it isn't a protocol that you will be able to pass across bridges.When I tried using 1gbps copper SFPs, I was unable to get the switch to stack; it complained the link wasn't 10gbps. I was hoping someone here might have experience, or eldritch knowledge, about whether I could use a cheap 10gbps SFP that might report 10gbps despite only being connected at 2.5gbps, and rate limit those interfaces to prevent drops. Anybody been down this road? If so, which SFPs do you like for this kind of adventure?