Do Not Do This!!!
I would advise anyone against doing this for two reasons:
1. The couplers are more prone to lose grip with one another. Many of you may remember the coupler problems I was having several months back with my unit train
, where it was prone to random uncouplings after the train stopped or slowed, and then resumed normal speed; there were breaks in the train in several places. Working with Kadee, who worked swiftly to resolve the issue, we narrowed the problem down to there being too much clearance between the thumb of the coupler and the knuckle face. This excess clearance allowed the couplers to "slip away" from each other, or slip out of each other's grip. As freight cars rock back and forth in all axis while travelling, and shift their positions relative to the cars next to them, the coupler bond must be *unbreakable* in all possible relationships so the train will remain coupled.
Bending the thumb of the coupler outward is not a smart idea, as it creates a *weak spot* and opens up a significant gap between thumb and knuckle. When BOTH couplers have that gap, the problem is exacerbated and it isn't hard to find a positioning of the freight cars that will exploit that weakness. With the physical dynamics of how our cars move and shift on the horizontal plane, no matter what the scale, you will almost always find the perfect positioning that will exploit the weakness in this bent thumb coupler idea.
Read the post I linked to above for more information. As it turned out, the problem was that there was too large a gap between the thumb and couplers. (I ordered all of these couplers at the same time, and they all suffered from a Kadee manfacturing flaw that has since been corrected) Harold is essentially recreating the exact couplers that were giving me problems.
2. What's more, bending the plastic thumb will weaken the plastic and, while you may not see any effects immediately, the couplers will eventually give you problems.
There is a reason these couplers were designed the way they were!