I'm going to put one 12mm double row angular contact bearing in - same as I used on the Z axis. Do you think that'll be sufficient?
iv put a 10mm double row a/c in my 2000w spindle but iv not used it to machine yet so i cant say for sure but as far as runout or play goes they will out perform standard bearings by a long way and as your going to get a kress at some point it would make sense to bolt a 43mm housing on the front of your brushless so you can swap them out easily and throwing a double row A/C in there while your at it wont take to much effort

my 700w with the pre-loaded(belleview washers) skate bearing gave a nice finish, i cant see them lasting to long but they are cheap and easy to change

ebay search "5mm slot drills (pk of 10) hss slotdrill uk made" £17 including postage
iv read HSS works well with delrin so i bought two lots of these