Wow! You horse is beautiful!
I would not do it. It is very dificult for a horse of your horses size to get up.
The bigger they are of course the harder it is. Even without you on top it is difficult. I have had three Clydes and the reason I eventually put everyone down was because of bad hips. They just couldn't get up any more. Draft horses have a shorter lifespan to begin with, I wouldn't want to do anything to shorten it any more.
Whenever I get off on a trailride I make sure there is a log or a ditch or some such to get back on.
These are photos of Sam when He was down in the stall and couldn't get up. I was lucky Missouri has a group of large animal rescue people that could come and help, otherwise I would have had to put him down that day, as I had no idea how or the means to get him up.
It was dejavue, as 17 years earler I put Seamus to sleep in the same stall for the same reason.
Anyway after Sam was up I knew he was living on borrowed time.
He lived another year, sometimes he got up after a roll sometimes I had to get the tractor out and get him up myself, I had bought all the staps and such I needed. He was never let back in his stall again.
I wish I had another Clyde.
I had to take the wall down between his stall and the next because he had wedged himself up against the stall wall. IMG_0039.jpg
The rescue group put Sam on a glide and pulled him out after the front of the stall was removed. IMG_0057.jpg
Then they winched him to standing position. IMG_0069.jpg