I run a 4 inch on my 23.You can stall the tractor if you put a 4 inch stick in thats very long 4 ft or longer[besides i cut my wood down to about 2 inch].Other then that brush doesnt phase it.
That being said id rather have a 6 inch if i thought the 23 could get it turning.You wouldnt have to cut all the crotches up in your brush so fine,and of course wouldnt be chipping big stuff,knowing i couldnt power it.My little SALSCO does a great job,but i have to do a good job with the chain saw ,when im limbing up my firewood.
ALAN