You do end up with wrinkles if the film is relaxed. This is good
I'd make filters for both both telescopes. I'd also make them for the finders and, any binoculars and even some simple glasses for naked eye viewing.
The more equipment you have equipped with filters, the more of your equipment you can use during the event. If the weather co-operates, I intend to photograph the eclipse through the 8" SCT while looking visually through the 12" dob, binoculars and naked eye (through filtered glasses).
To make a finder/binocular filter is much easier. These don't have to be perfect so I don't spend a lot of time on them.
I first cut a strip of cardboard about 3cm wide and about long enough to wrap around the finder/binocular objective 1 1/2 to 2 times. Wrap this around the finder/binocular objective and secure the end with packing tape to form a ring. Then I cut a second strip of cardboard the same length as the first but about 1.5cm wide. Wrap this around the first ring and secure the end with tape. The outer ring should slide easily over the inner one. Take the outer ring off.
Now cut a square of the filter material, put it over the first ring (still on the objective) and slide the second ring over to secure it. Roughly cut away excess filter material and use packing tape to secure the whole thing together.
Make sure there isn't too much damage to the filter material. If any pinholes are visible (and are stressing you) they can be covered with a black felt marker pen.
Hoping the weather improves for the eclipse
Have fun,
Doug