Hi Robin,
A Happy ad Healthy New Year to you to. I frequently use a Loctite type adhesive to hold cylinder covers in place, using mostly non Loctite products just high strength versions. As to depth of shoulder, I use 1/2 mm say 1/16" on up to 1/2" bore after that I use screws. I think for larger bores a deeper shoulder would be an advantage with an increase of face area as well particularly if you are using higher pressure. I have never read anything on the subject, I expect Loctite make a a higher temperature high strength product but I have never checked. So far I haven't had any failures with what I have made and done. Maybe I shouldn't have written that.
Take care Tony.