Yea, i think thats the normal size for the leaves. they are maybe a little smaller than my fjellheim. A few years ago it grew a lot in one season and has now slowed down. i think it will fill out more this year. I'm not 100% sure the 'mother' tree was a sango but it does seem to have red bark.
the original witches broom broke off in a snow storm this last winter. i have one grafted thats now in a 5 gallon pot. it put on a lot of growth in its 2nd or 3rd year and is now filling out. kinda has little bunches of leaves on long branches. my maple hobby has taken a back seat to other interests lately so i haven't been grafting any new plants
Thanks for the update! Interesting, to see the genesis of a new variety. If you think of it, I'd love to see a picture next spring.