My old horse had them and they never really caused any issues - he needed a fly mask with ears, and didnt particularly like you messing with his ears, but aside from that I often forgot he had them until a teenager asked why his ears were going mouldy 😂
Provided I didn't want to show etc it...
I currently have two - the jump from one to two was fine, but honestly I've made the jump to 3 twice and both times I have found it absolutely too much, especially with working full time.
Definitely consider what you would get from #3 that you aren't getting from #1 or #2, would be my advice
For what it's worth, my 14.1 highland was on the weigh bridge this weekend and was 580kg, with a body condition score of 3-3.5, and is also long enough in the back to take a 17/17.5" saddle - so they do exist.
He is wide so maybe not the best for stuff hips, but I'm 5'5, chunky, and short in...
Mine is a miniature Shetland but he has the partition out, we have made a barricade which attaches to the full width breast bar, and he's tied up under his chin to travel (and he chooses how he wants to stand, which is normally herringbone)
I also tow with the 2L AWD Kuga - it has no issues with my pony (570kg) and Shetland (170kg) and my trailer (900kg unladen) up and down peak district hills, but like dottylottie, I wouldn't want to put more than that in it!
Fuel economy also not too bad as a towing vehicle and a daily vehicle...
I'm a big fan of using a full width breast and breach bar for travelling one in a double trailer - plenty of room for awkward loaders, tacking up, booting etc and otherwise hiding inside on rainy days 😂
I have an August baby, he's just turned 4 but still very much looks like a 3 year old - he's a late maturing breed anyway so I'm assuming he will catch up in his own time!
I tow with an AWD Ford Kuga - generally only have 1700kg maximum in the back and it has a capacity of 2100kg, it's not struggled yet with our big hills and is very easy to park in car parks/economical to drive.
I'm currently towing with the AWD 2.0L Kuga (2100kg towing capacity) - generally only take the trailer (900kg) and one horse (no more than 600kg) and it doesn't struggle with the peak district hills (until I tried to use cruise control after a bad run up at the large hill on the way to Beaver...
Game changer for mine - he's on 1 tablet a day, his fat pads and crest disappeared, he became happier and more alert, no longer drinking an entire bucket of water a night.
It took him about 2 weeks to settle with it but he went a bit lethargic for a few days, low appetite etc - some suggested...