Last box drill I had was 42' of IHC 7200s with a transport hitch. Drills held 2.25 bu. / foot so filling them involved 94 bu. of seed. Good luck filling them in less than an hour if all you are using is a shovel or bucket. My drills had zero electronics. They used a reflector mounted to a conduit lever that bobbed from an eccentric clamped to the feed shaft. Drills had a small window to sort of monitor how much seed was in the box but if you plugged a run you would leave an un-seeded row until you stopped and walked the drill to check. Drills were wide enough and close enough behind the tractor that parallax was a problem in judging distance to the last pass. Of course, all of this was further complicated by what a dusty day would do to your vision of all the critical things you were supposed to be watching. Couple this with the inherent inaccuracy of metering seed through a box drill vs. an air seeder. Yeah you sort of got the job done but it was no where near the best possible. And then there was switching the drills to transport mode. Took quite a bit of time and several trips in and out of the tractor. Plus, the drills were supposed to be less than half full before transport or the transport wheels wouldn't lift them.