pruning an overgrown winged eunymous

It's been unseasonably warm here in my Missouri zone 5 region all winter and everything is starting to wake up already. I'm trying to get a head start on the yard by pruning this monster 'burning bush' in front of the house. It's, I don't know, seven or eight feet high, taller than me by a lot anyway. It seems to grow about 3 feet a year, and keep trimming it every year, and I swear it grew an entire foot over the winter...
Anyway, I've thinned out three or four of the oldest branches by cutting them at the ground (I no longer have branches coming through my livingroom window, for example). I still need to take height off. I'd like to bring it down to about 4-5 feet high but I notice there are no small branches (suckers?) or buds at that level.
My question is, how low can I cut it and still have it leaf out?
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