I regularly travelled a chunky 16.3hh in a 505 without the partition, with a partition it would be a real squeeze.
The other thing to consider is the headroom, you would want a calm experienced traveller if you were to consider it as there isn't a lot of room spare above their heads.
It'll be a bit of a squeeze because of head room, will also depend on what type they are, whether a calm or likely to jump sort. You'd definitely need to travel alone without the partition and cross tie so they could travel diagonally if they wanted.
Chloe is only 15.2, but wide and long and it was a real squeeze for her in the 505.
With a partition we couldn't use the back bar, so had to rely on her not backing out whilst we put the ramp up, and her sides were touching the partitions. I think they recommend up to 16.2hh for this model.
well I put my 17'1 in a 505 with a 15'2 on the other. Not an ideal situation but it was an emergency. Little head room and he had to have the bars on maximum length but he went in and travelled fine. Mind you he would get in a caravan if I asked him nicely and never throws his head. he normally travels in a 510 and there is loads of room in there for a couple of 17'2s
I'd say not. I travelled my youngster in a 505 once but found she didn't have the head height and, being an inexperienced traveller, found exiting the trailer a bit tight (loaded on driver side). I bought a 510 which is great and plenty of room.
My 16.3Hh ISH goes in mine, but its not ideal and we are looking to change it for a 510. He travels with the partition in and travels very well, but its tight, particularly trying to get him out of it!
We bought a 510 for ours even though they are small (13.3 and chunky and 14.3 but still growing) just for the extra headroom. The extra width is a bonus, but the 505 really isn't very tall.
Ihave travelled two 16.2hh quite easily and happily in my 505, if they are seasoned travellers then i would say you would have no problem, it can be a little tight getting them out though on the side closest to the front ramp, i always put the larger horse further away from the front ramp and that was fine.