This November I decided to do as much no-stirrups work as possible to build up leg muscle to improve my riding. I got a coouple of friends to do it with me and it was super fun (and painful!). I couldnt do no-stirrups all the time, I rode with stirrups on new horses and at shows. Basically, every day I had a lesson I would ask my instructor what I could do with no-stirrups and then do as much as possible! It didnt seem like it was changing anything but just recently my instructor had us two-point around the ring and at the point my legs would usually start to hurt, I realized that my legs felt much stronger. This has made my leg more quiet, my jumping better, and has just made my riding much better.
I only did a little extra no-stirrups work, yet it made a huge difference! I strongly suggest you guys try doing it. Pick a month and do as much as possible, you will see a huge difference!
When you are done you will be very happy! Let me know how it works out!