I would think it is your decision. I was going to teach my horse to bow or even lay down when she is older so I can get on bareback easier, although she is a quarter horse, not a clyde.
Have you heard of Stacy Westfall? Is so, Her horse Roxy (roxy died a few months ago though) was trained to bow while Stacy got up on her. She was a quarter horse also, but it still worked.
I would say, it is safe as long as you are not constantly doing it (like 4-5 times a day) but if you did it like 2 times a day, or less, it should be okay.