Hi Jethro
The mirror cell can be pretty simple for an 8 inch mirror. The stellafane design I’m sure works well. I like and recommend this one:
https://garyseronik.com/a-simple-dou...our-reflector/
I’ve used this design on four 8 inch telescopes and I find it holds collimation extremely well. The only thing I have changed is that I don’t like using silicone to attach mirrors. I made some simple supports with angle brackets and plastic bolts. If you are interested in the details let me know and I’ll post some pictures.
Buying the skywatcher truss seems a very expensive way to go, especially since you will then need to modify it for a longer focal length. If you go the truss route there are some simple ways to do it without all the fancy brackets. The most obvious is to make 4 pairs of truss tubes joined at the top like in the photos below. The bottom tubes can be attached via bolts and wing nuts through a hole in the mirror box.
Hope that helps.
Rod.