Sorry you've lost me
I was laying out that Matte Boxes and one set of filters can be a money saver compared to buying a pile of screw on filters!
Sure Red and Scarlet are 'cheap' - I agree with that
As for not banking on the FS100 for bigger jobs Id agree with that too
In the end I'm not sure I want the mattebox. In fact I'm sure I don't want it after considering all the aspects. I recognized it's super usefull, practical and fast and a must in cine practises but I rather to follow another route.
Probably 2 good zoom lenses that cover the all range with 2 fader ND permanently mounted on them would do the job. I hate to screw (no pun) but I prefer that to weight.
The irony is that I spent my all life with prime mentality and know very little about zooms. I ignore what are the good ones suitable for Red-Canon affordable. Of course, with unlimited budget you go Angénieux and you're secure, it's top, but I don't have the budget for such gear.
What was this IR filtration with ND filters on Red ? Another oscur complication on the chain ?