I've never liked the huge size of the Gilbert knuckle couplers; compare it with a Lionel "lobster claw":
Look at the difference in car body width ( 
) yet the 1/64th coupler is only marginally smaller than the 1/48th.
Here are (2) Gilberts connected:
There is 7/8" distance between the cars.
Here are 2 with link couplers connected:
Here the gap is reduced a full 1/4", down to 5/8". Even though these link-types do look rather silly, this reduction in the gap is, I think, reason enough to not dismiss these out-of-hand. Plus, they have that "old school" look I find charming... 
This is #302 tender with a Kadee O scale coupler installed, connected to a standard Gilbert knuckle:
To my way of thinking, the O scale Kadee looks to be the "best" compromise.
I'm gonna be gone for a few days; am curious to see what comments (if any) this generates...
Talk to you next week.
Mark in Oregon
PS: Happy Mother's Day!
