Michael,
The way you had the reins on before showed an extreme shortening on one side and slack on the other. Given how you had the bit rings pulled back on the horses mouth and the shortening of the rein on one side this would imply that the rider was pulling back on the left rein and the horses head would be pulled a little more extremely than what you had. When riding, you grip the reins in the center. Your previous sculpt was doing the opposite. My advice would be to put some slight slack in the reins and leave them relatively equal to imply that the horse "has his head" and is turning it naturaly. Or slightly have them pulled over to the left. Trained horses don't need much to make them turn. Most of it is done via leg placement and pressure. I move my horses around using only leg and use reins to pull them up for the proper lead for cantor or gallop and or to make extreme turns.
The photo reference regarding the bridle from the SCA site is good but not correct in that the woman has the throat latch too tight on her horse in the reconstruction. The throat latch is not really all that necessary and is there really only to keep the horse (or rider) from pulling the bridle over its head by rubbing or having it pulled on when the head is down. Since it goes over the windpipe and if pulled up too tight it can restrict the breathing of the horse, especially if the horse is galloping or in this case charging. ( as a side note, even today in eastern europe and parts of the middle east they still "slit the nostrils" of horses, donkeys and mules in the belief that they will get more air and breath better under periods of stress) so it stands to restrict the windpipe in any way is not desirable. While I understand the reference that Roger was providing, it is flawed as too many things are that involve the SCA and its quasi form of history rec-reating and not re-creating. Though the period references he included are great for reference, they are also flawed in that they are artistic representations and not necessarily true to life. Though there are a few that depict the proper adjustment of a loose throat latch.
If you are going to do more horse equipment and are looking for reference, I highly reccomend the Museum of Londons archeological survey of The Medieval Horse and its Equipment. Where the reconstruction of the bridle on the website provided by Roger is what it is, the hardware or "furniture" (rivets, buckles etc.) are modern and not medieval. There is a difference. In some cases albiet small, but in others rather alot.
I like what you did on the fix and it looks much better and more in proportion. The saddle seems in the proper place now as well. I hope I was clear enough about the reins. If not let me know and I'll see if I can explain it better.
Regards,
Mike