cyclingarri

Ive been working on a Fd shimano nexave tz301 and the limit screw heads were stripped. Also even reaching limits of screws seems to need just a little more. Another possible issue could be that this front derailleur initially came with something called a "pro-fit alignment block" that is no where to be found or even to purchase. So instead im using a wedge and regular longer screws. Could there be a chance anything can go wrong using the reg. screws and using a plastic piece as a wedge for installation?

Andrew R Stewart 

When Shimano came out (late 1980s?) with their plastic set up aids we tried them. For a inexperienced wrench they did help get the alignment really close but for us old grumpy guys (I was old and grumpy even back then) we found them to only add time to out positioning the der. These days many of their ft ders are packaged with a insert block to lock the cage about halfway through it's in use travel range. Again for some this helps. Others toss them out before installing the der.

As to the limit screws- I wonder why the OEM travel range isn't enough for your needs. I wonder about the number of rings you're using, the chain line and what other subtle issue is going on. But the screws typically are of the same threading and can usually be subbed with most any other limit screw, length dependent.

I don't bother to keep up with Shimano's latest set up gizmos so I'm possibly missing the boat here. Andy

dsbrantjr

Your limit screws will last longer if you relieve the spring pressure while adjusting them. Using those tiny screws to drive against a strong spring is asking for damage.