Morning, at least it is here.
I'm running into the same situation and I haven't got it set up yet.
My router dust collector is 1-1/4, Vac is 2-1/2 and fence is 2-1/4 or something. Doesn't fit the shop vac very well, still working that part out.
The idea I hit on and the direction I'm working is using about a 6" length of 3" thinwall PVC, capped at both ends and running the Vac to one end of it and the two dust ports outputs into holes drilled along the length, essentially making a manifold. The advantage being that, since I'm making the holes, I can make 'em any size I need depending on whats available. Also, as the hose to the router doesn't need to be that flexible and will help hold the manifold in place. I have a portable benchtop with foldup legs so haven't got a good place to anchor it. When I get around to building a cabinet for it I will incorporate the dust collection into the cabinet.
The problem with experience is I usually get it immediately after I need it.