It is a bit of a bugger to work with. Getting a good edge is very difficult. You need either very sharp scissors or as pointed out by RR you may be able to use a sharp Stanley blade if you can adequately clamp the material as you cut it (otherwise it pulls and comes to bits). The other issue is having the stuff stay together once cut. Many of the cloths on the likes of Amazon, etc are sold are very loose twill cloths with large fibre bundles for laminating and the like. As such they fray almost instantly and are virtually impossible to edge. For what you're after you need to select a woven cloth. These are more like the stuff you'd make clothes out of. Although I've never tried doing what you're thinking of doing I suspect that to achieve any kind of life before it all frays away you will need to sew a hem round the edges. And on the knees where its subject to a lot of folding and scuffing I think clothing adhesive will struggle. With any cloth really but in particualr with aramids as they are relatively 'slippery'. Nicky's option mught actually be th best for this application. However I'd be interested to hear how you get on.

Actually Ian , i have referred back to your photo, I can see you have the side port connecting to the old thermostat housing and from the engine. The second port on this side returns to the bottom hose. The port on the other side to the top rad hose .  

Not sure, i was following your installation (perhaps wrongly), i figured the straight one would be feeding from the old thermostat housing toward top of rad in a straight run when open but when closed looped back to the slanted pipe. Although could have that wrong way around!  

If you mean the thinner pipe from the top of the thermostat it was designed to go top of thermostat housing to the header tank

A sharp Stanley is as good, we work with kevlar all the time.

I think that is teh wrong way round. The hot water flows from the top of the engine to the top of the rad. I think the smaller hose is a bypass that goes to teh bottom hose when the thermostat is closed? The way it is currently connected it will not do anything. Happy to be wrong....

Have you got the remote thermostat connected up properly? On the side with two spouts, shouldn’t the straight one be going to the bottom hose?     thanks Ian

No, Colin, but I think you have! The only thing I can think of that might scupper my cunning plan is cutting Kevlar.   Special scissors/knife needed? John

Here we are cobbled together. So the thermostat return heads to the bottom pipe before the pipe. A T piece in the bottom pipe connects these 32mm pipes. Above this is the 19mm T pipe which leads to the headder. Above this another T leads from the heater. This T then goes to the thermostat. I didnt have space to put two T pieces in the bottom pipe so the 32mm one it was. The header tank does feed to a lower point. The top of the rad is blocked off where the header fitted

https://www.youtube.com/shorts/eH5rnXoC4PI