I think you are walking with him too much, you need to try to stay in one spot and try to have him circle around you. But I'm not an expert by any means, I am just a beginner too... But he looks great! Moves pretty (IMO) and defiantly put some more weight on that boy, he'll be gorgeous!
If you are going to stay stationary in the middle I would suggest a longer line but he looks good ... he is def still skinny but you know that because you said you are trying to get weight on him. I would say keep up the work and working on a lunge line is a great idea and will build muscle along with his weight gain which will help you a lot in the long run. He is very cute tho!
Thanks he was moving in a nice circle but the only line I have is a bungie one and as soon as we would feel the tug and release he would stop. He has great manners in that department but it made it hard to stay still. I just had to switch it up a wee bit cause he has been getting bored with stretching and just round pen work. I would say he looks 10x better since he got sick he weighed about 350-400 lbs soaking wet. Thanks for the tips and the coments it helps to have others let me know what they think would help with weight and muscle gain.