Thank you for the ideas/input.
Both the tent fabric and the patch fabric have one side that is 'matte' and one side that is 'shiny' ... I assume the shiny side is PU coated. When I first attempted to patch I put the Silnet on the PU side of the patch and then applied to the matte side [front] of the tent fabric. I then clamped-it between to square pieces of ply for 24 hrs. The patch peeled easily. As mentioned above, I then tested gluing PU side to PU side with Seam Grip and then clamped for 24 hrs - peeled even easier.
So, from distilling your ideas, I would need to either:
1] use just normal, uncoated nylon and Seam Grip - then clamp/press.
2] use the [potentially PU coated] silnylon I have, but smear a thin coat of Silnet on both surfaces, wait 10 and adhere - then press/clamp for 72 hrs.
Are there any adhesives that would work without question - like Hysol U-09FL? It's used with cuben all the time, what about silnylon.