Having had various helmets for different activitys...
There is no substute for a proper trials helmet. The Hebo that fits my head is so comfortable it is crazy. I can really wear it all day and never even think about taking it off. There have been times I rode all morning, stopped for lunch and while eating I realized the helmet was still on. I forgot it was there.
While riding, you get your stretching in for the day. You will twist and turn in all directions. Even in the novice class I am in. As for crashing (especially in the entery classes) it is nothing more then falling down. I had worse crashes as a kid on a bicycle. The brace and MX helmet will probably cause you to crash more due to limited visibilty and limited mobility.