Unless it's peeling or bubbling, strongly consider letting the Mylar do it's job; protecting the playfield.

Have you ever removed factory mylar shields from a playfield before?
If you have not, doing practice on an original playfield is not a good idea.

The ones around pop bumpers, slingshots, high traffic orbits are there for a reason, and sometimes the glue adhesive has been sealed to the the clearcoat for a VERY LONG time.
On non-clearcoated playfields its almost always a disaster.
It takes a LOT of patience, heat cycling, goo gone and sometimes even nalpha.
If you rush which many do (or even if you don't) disaster can still strike.

*Danger* Will Robinson! *Danger*!

Freezing works good but I agree with the others leave it be

I removed all the Mylar from my gnr. I used the freeze method. Worked great.
However, I have had issues with other Mylar on other games. just because it came off flawlessly on mine, doesn't mean it will on yours. I'm not an expert but I'm thinking the environmental conditions the game has been in over the pat 20 years may be a factor of how well the Mylar and glue comes off.

I use industrial strength Citrus D , big undertaking but patience is the most valuable factor... Have done 3 non diamond coated playfields with this method , and no other playfield damage!

I just removed mylar from a Bally 6MDM in preparation for extreme touch-ups and eventual clear. Mylar consisted of two sling moons and two pop bumper rings. I wouldn't wish the removal process on my worst enemy. Canned air to freeze the the mylar plastic off first...it peeled right up and didn't take any paint. I then soaked the area with Goo Gone, covered with a paper towel and let it sit for a half hour before adding some flour on top. Persistence was key after that point. A credit card/gift card worked to scrape off the goo in some areas, loosen it more than anything, but I found that harshly rubbing my finger over the area helped roll the goo/flour mixture off a lot better. I had callused fingers that were numb for hours, but it came off! Set aside an evening to do it. I don't envy doing Sys11 games or later....good luck! Many of my games from that era have original mylar that have seen better days...and I think they'll stay that way.

I left the slingshot semicircles on my WWF. They are not that noticeable to me and you can buff them to pretty nice shine if you are going to clean the PF.

I find this method very effective. After using freeze spray to remove the mylar I first get a small bowl with a little flour in it, dab my finger in it and pat the glue as flour readily sticks to the leftover mylar glue. After that's all patted down with flour I pat in some goo gone spray gel and let that sit for a few minutes. Pat on another layer of flour and starting rubbing it with a finger and the glue combines nicely with the flour and is easily vacuumed up.