Iāve had both long and short-billeted saddles; my real preference is for the āuniversalā length billets as I can use girths of various lengths and I wish I had them on all my non-monoflap saddles.
For my small, round horses, Iāve found that the longer girths (in effect, using the universal billets as though they were short) stabilize the saddles better. One of my instructors, a BHS Fellow, told me that she agreed when I discussed this with her. I believe, from my experience, that having a longer girth buckled relatively high on the curve of the ribs works better than having a shorter girth buckled lower on the curve with a round-barreled horse.
However, I personally donāt have an issue with feeling a lump from the billets/girth and I think thatās either because of my anatomy, my saddle choices, or a combination of both, so there is no discomfort of mine coming into play.
Tightening a short girth on a monoflap, from the saddle, has been possible for smallish me because Iām flexible, but Iām not thrilled about doing so, as I feel as though Iām in a more vulnerable position than when tightening a long girth. And, with my small horses, itās been more challenging to find appropriately-sized short girths. However, for a couple of them, a monoflap saddle has been the best fit.