Window Covering Replacement Questions

I have read a number of threads about replacement of window coverings. I would like to replace my shades with the cellular shades that have half blackout and half sheer. Are there some brands that will not work because the header is too wide to fit in the space between the window and the window cover in the motorhome? How easy is it to attach the header to the wall of the motorhome? It seems the walls are not that thick and you may have issues with the bracket holding. Is there anything else I should look out for?