You're Correct!

Having a too flexible shaft in your driver will often feel out of control. There will be a lot of inconsistency in your ball flight and strike pattern.

Your shot dispersion will be very wide as a result of these inconsistencies and varying strike location. You will see all kinds of ball flights, from high to low, and from left to right shots. As your club speed and tempo will be putting too much force on the club shaft as you swing, the shaft will be flexing too much which has an effect on the club heads delivery to the golf ball, hence the inconsistencies in the balls flight. You will have a tendency to see balls which launch high with too much back spin even when struck out of the centre of the club face.

These shots will therefore fall short in distance as they are not launching with the optimum launch and spin rates to maximize distance. To find the correct shaft flex for you, it is best to have a custom fit session. During the session you are searching for a shaft which will deliver optimal launch and spin rates while doing so consistently on those centre strikes.

Another note to make is that all regular, stiff, and x-stiff shafts are not all the same stiffness and vary between shaft manufacturers. One companys regular might play softer or stiffer than other brands same stated flex shaft. If you are spraying your drives with really inconsistent flights, you should go and have a custom fitting to find which shaft is right for you.

A ball that squeezes out very low and to the right is a sign of a shaft which is too stiff. There will also be a very harsh feel as the shaft never gets loaded. If you experience very low and right drives, get your shaft checked by having a custom fitting session.

If the shaft in your driver is too flexible you could well find you lose some distance but this is not the only thing. You will more likely see an inconsistency in distance in a shaft which is too flexible. Some drives will fly long and straight, some short and crooked. As the shaft is too flexible there is an inconsistency in the club heads delivery, which causes all kinds of misses and varying distances.

If you are producing a ball flight which is of a consistent trajectory and distance then you most likely have the correct shaft flex for your game. It is always advised to check your equipment by visiting a custom fit centre to get the correct equipment in your bag to help your golf game.