I think that a top mount is indubitably the best mount position. For those who may have vertical space limitations this has worked for me (five Spools of PETG with 0 Tangles… so far). The Rollers are adhered to a short piece of 2"x6" using very flexible auto/plumbers product GOOP. It’s very stable.
Looks like a good setup. 
Mine is mounted on top ( temporarily ) as it’s easier to change filament there but at startup before a print the extruder moves all the way up and then back down so I have to watch to make sure the filament doesn’t catch on anything while it’s doing that… 
On both my V3 SE and KE I have a filament dryer in that position feeding the printer. Just about see it in this picture.
Added some gantry supports too, think I might add those to the KE also.
Are those threaded rods the gantry supports…? Looks very sturdy…!
Should be sturdy they are OTT M10 threads. Will be fitting them to the KE too when it stops raining and I can be bothered to go to the shed. The KE version also has brackets for the Nebula pad and the LED light. here is the link Does need drilling of 3 holes on the left of the unit, Ø4.2/4.5mm to accept M4x10 screws/nuts.