There's a lot of discussion around here about using shells of different length than the chamber.
Nobody's ever happy.
The shorter shells may well work, depending on recoil impulse. Try it.
If you have the old spring, that might be the perfect place to start fine tuning it for lighter loads. I've not done it, but maybe chop a turn off the old spring and see if that works.
I would caution you to not just remove the friction piece. That controls the speed of the forward stroke also, and removing it can be hard on the forend wood. I think that's one reason there are so many split ones.
