If you give your large bees the choice (with foundationless) they will draw out large cells and lots of drone cells (in the spring) everytime. If you want small cells, probably the easiest way is to start putting in some of the Mann Lake PF series of plastic frames. They’re 4.9mm cell, or maybe 4.95mm I can’t recall. Large bees aren’t thrilled to see those frames, but if they’re waxed well the bees will comb them out. You have to be diligent though because about 2 times out of 5, they will ignore the PF pattern and do their own thing. Just scrape them down and tell them to try again.
Not a big fan of small cell myself, but the frames are cheap and this seems like a fad other beeks want. I have about 1000 pf frames in use.