Monte, I am betting the cams that work don't increase the overlap event. If my theorizing is right, then the tight LSA with less duration on both lobes makes the overlap event shorter or close to the same but with higher lift to compensate, providing the same "window" for scavenging. Of the three cams I have for my motor, the overlap period is very close to the same, with the main change being the exhaust opening point.
A motor like mine may respond to this because I have 80 percent exhaust to intake flow, and might be able to cut the exhaust duration I run way back for that reason. An all out motor sacrifices exhaust flow percent to allow for a bigger intake valve, and makes it up with exhaust early opening and duration. And like you said, put a cam in and find out. I plan on that with the next tear down. My current cam,
282 296 112lsa duration .775 lift int, .685 ex. .200 numbers 203 ,206
time card at 108
intake opens 33 close 69
ex opens 84 close 32 overlap 65 degrees

New cam?
278 278 106 in at 106- switch from 1.5 to 1.7 rockers
intake opens 33 closes 65
exhaust opens 65 closes 33. overlap 66 degrees.
The big difference is the exhaust opening, with 18 degrees later event on the exhaust of the narrow cam. The intake close on the narrow cam is 4 degrees earlier. The high ratio rockers will increase the .050 and mid lift duration and compensate some for the overall shorter duration.
My biggest concern is not having a big enough cam core for the lift rates I would like to run. Also I still have stainless intake valves, which don't help. The one thing in my favor is I want to keep the shift points the same, 7100.