[Roadsters] Differences in carb piston damper rods?

[kendelmccarley at cox.net]

I've been working on getting a '70 1600 running that was missing a damper and cap from one of the carbs.  Joe Russo was kind enough to fish one out of his stash to sent me but, after installing it, the car still runs poorly.  I pulled the air cleaner to check the rise and fall of the carb pistons.  Sure enough, one of them was much more resistant to movement than the other.  When I switched the dampers from carb to carb, the one with Joe's part was harder to move.  

The only difference I can see between the two is that the one Joe sent me is around a sixteenth of an inch longer, putting the damper part farther down into the carb.  How does this make a difference?  If I mod the new part to be a bit shorter (pull it out of the cap, cut it down, and re-insert into cap) will that cure this problem?