I regularly shoot 8x10 Tungsten film using a P2 & Schneider 165/8 SA lens wide open (environmental portraiture).

To correct the Tungsten film to daylight I use a 100mm 85b filter in a Lee filter hood attached with a 105mm adapter ring to the front of the lens.

I've noticed that in any circumstance where I need to use movements, typically rise/fall, that there's noticeable vignette on the slides - it's not very easy to pick up whilst shooting as I'm usually somewhere cramped and without great lighting.

Is there any simple way to mount this filter to the rear lens element which has no filter thread? I'd consider even just taping it on...

I'm looking for an inexpensive option. Tiffen 105mm 85b's are ~$350, and a Cokin X-Pro filter and holder is not far behind.

Has anyone had any luck taping gels to the rear element? I've got about 3 square metres of 85b here.