Thank you Dean and Brian for the praise, I'm honestly just doing things under my nose as I go along...
I stumbled across this youtube channel "astronomyshed" by a gentleman from the UK who modified his focuser by increasing the contact patch by sanding/filing it with a sharpening stone.
https://www.youtube.com/watch?v=ofOSAMlqZWw
He depicts the issue that the shaft only contacts the edge of the focus tube's slot and thus a poor surface area to exert the friction upon. This image was from his youtube video but I had the exact same marks embedded on my focuser prior to his suggested mod.
http://www.iceinspace.com.au/forum/a...1&d=1519263994
So that sent me on a quest to follow his guide by dismantling the whole focuser assembly and I was glad I did. There was a cake of dust between the crayford shaft and the teflon sleeve which Im guessing caused some of the slipping problems I initially had. After a good clean:
http://www.iceinspace.com.au/forum/a...1&d=1519263994
Close up of the new contact patch shows that the shaft now glides along a much wider surface area. It feels significantly more secure with less tension on the grub screw. It can also comfortably hold a 1.2kg camera without slipping down, without the locking screw! The smoothness is about the same. Also, you can see flock tuffs stuck on there randomly... what a nightmare it is to clean those off as the static just attracts it back (everywhere!).
http://www.iceinspace.com.au/forum/a...1&d=1519263994
Not sure why skywatcher decided to use this glittery silver for the focuser tube apart from external aesthetics... but one would guess it'd be no good when it protrudes inside the OTA. Time to flock that as well but care must be taken to mask out where the bearing guides run to ensure smooth operation.
http://www.iceinspace.com.au/forum/a...1&d=1519263994
Focuser flocked and reassembled... not sure if itd make any difference at all but its done
http://www.iceinspace.com.au/forum/a...1&d=1519263994