I have flexi reins for my 5yo and I really like them, although he is not bolshy! They remove the 'fixed' point of contact and as such limit what the horse has to pull/fight against. Defo worth a shot!
The ones I have are inserts that you can use with normal reins. They help the horse to soften and help you maintain a more consistent contact. They also absorb any unnescessary movement on both sides
Yes - in a good way. My last horse (TB) would constantly fight, snatch at the contact and would never soften and relax into an outline. After months of struggling I had almost got him somewhere near accepting a contact in walk and trot but never in canter. Read about these and thought they would be worth a go. Not exaggerating - not only did he engage in walk and trot willingly from the very first time I used them, he also softened in canter for the first time! (Had owned him around 2years by this point!) Rode in them in the school for a few months and then went back to his regular reins. We honestly never looked back.
I made the mistake of selling my last lot as I felt we didn't need them any more and have recently forked out on a new pair for my youngster! Saw cheaper versions on ebay but they didn't look as though they had as much elastic in them so went for the dearer ones - new ned is happier already.......