Quoted from GorillaBiscuits:

I had great success using wire snippers to shave off just a touch of the plastic on each side (at an angle) with Comet retros in the GI for mine. I kept the original white plastic sockets, and it was a nightmare to try and squeeze them in before doing that... after my modification they all slipped in super easily and the end result was very much worth it!

Quoted from phillyfan64:

If you are keeping the original linear flippers:
https://www.marcospecialties.com/pinball-parts/P-6264-134

Quoted from slochar:

There are 2 versions of that plastic. The one they sent, and the other one. They are both "correct" but IMO the swiggely one is better since it lets a ball that happens to get behind the single drop come out.
You might have to make it, well over 10 years ago you could get just the clears from marco, but I don't think they are made anymore.

Absolutely. IMO linear flippers are shit. I know why they were made originally; they last a LONG time on location without maintenance. (i.e. they will still work even after the parts (mainly the nylon button) get worn.) There's a lot of moving mass to them so effectively makes your flipper weaker. Also, the parts to replace are a lot more expensive than the earlier style.
I change all my linears to the earlier style automatically, I don't even hesitate when rebuilding them. The linear baseplate can be reused on the earlier style easily.

Linear flippers have a long metal plunger with a notch in it look at your flipper mech if you have that, it's linear. The other style is a brown fiberboard link.