This link has a diagram showing the different parts of the headstall. The part that is actually called the bosal is the nose piece. It's very stiff and I'd say the only concern is that it may ding Blu's nose since a white nose is easy to mark.
Saturday I spent a lot of time in the saddle. Probably 3 or 4 hours. Only an hour of it was actual riding, during my lesson, but the rest of the time was totally nice. We'd stood for hours and he didn't move - and I mean didn't move. He wasn't fidgeting or moving his feet the whole time Sharon and Emilie were getting their lessons.
Emilie was first up, riding Rocky and working on flying lead changes and pattern work. Because the workout was so intense it could only be done a bit at a time to give Rocky a chance to rest up. So when she finished it was Sharon's turn on Nazz. Once Sharon's lesson was done, Rocky and Emilie were on again. Then it was my turn with Blu. (I wore gloves this time - no holes in my hands from the reins this weekend!)
Remember when I mentioned that Blu challenged me a bunch and we figured that by me meeting his every challenge he wouldn't do as many challenges next time? It appears to be working. There were probably only 10% of the challenges and they were minor. And his spook level is super low, too. At one point I was going into the lope heading towards the side of the arena that has the giant hedge that has a road behind it. A truck pulling a trailer drove by going the same direction we were. You can't see the vehicles on the road, just hear them. It sounded like a big metal trailer full of loose metal parts because it was making a RACKET. We were keeping pace with the truck and trailer and not only did Blu not spook, he even picked up the correct lead. Awesome! And while we were finishing up our lesson Sharon and Emilie left the arena with Nazz and Rocky and Blu was left by himself. Horses don't like it when every other horse leaves the area, and I'm sure he knew they were going to the barn. He watched them leave yet still kept his head on the job. I was so impressed with him. I tell you, he is really becoming a bomb-proof gelding. And we're going to work hard to keep him that way!
This video was from Sunday morning. I used my phone to take the video.