Yeah… yours is a great printer. Great work on that. Beautiful build. but I am pretty sure your uses a 1.75 mm filament hot end.
If he uses my 3 mm filament hot ends he will need to either use a Bowden system or some sort step down direct drive. That’s just the way it is with 3 mm filament. The pressure required for 3 mm filament needs to be stronger to get it through a nozzle. That is why most people (Like me) are moving away from 3 mm to 1.75 mm filaments on their machines. I know you know that already. I say it here so others know it as well. In any case I found this on thingiverse so it would not involve CAD work to get running with a Bowden setup.