Durst 138s - Problem with Nega 138 carrier

I've got two Nega 138 carriers, and they both have the same problem: They do not apply enough pressure to keep the negative properly positioned. Does anyone know a fix for this? Do I have to replace the 'tabs' on the bottom perhaps? Maybe the 'flat springs' (for lack of a better term) on the upper plate?

It may sound trivial, but when I'm trying to do a wall projection, the negative strip (120 and 35mm) wants to slide out. I can tape it down, but that's unacceptable with glass carriers.

Any help would be great. I find that you can make all sorts of adjustments to the chassis of the 138s, but the carrier doesn't seem nearly as well designed.

Thanks!

The glass thickness might be a factor. Focal point makes 2mm and 3mm glass so if you could replace a 2mm sheet with a 3mm sheet, that might solve your problem. I use a G139 enlarger and I bought a like new Trineg carrier which does not work with this enlarger, I was sorry to learn. If it would work for you, maybe you would consider a trade. Negatives are held firmly in place between the two glass sheets. Glenn Evans told me the Nega 138 is the one I need.
Ron McKinney