I also have a V drive. Beta, my engine builder highly recommended that I fit a flex coupling.

The Vetus type 6 coupling is not a drive saver, it is the same length as a standard coupling so no shaft mods are needed.

When an engine with a V drive moves under load there can be quite an angle change. This puts a load on the transmission bearings and will accelerate wear. Once the bearings have worn replacing the seals does not stop the leaks. I also have very stiff engine mounts but every engine moves from the thrust transmitted to it from the prop.

Interestingly, the coupler cost a lot more not machined for a shaft than machined. So if they do not sell one that fits your shaft, buy one with for a slightly smaller shaft and take it to your local machine shop to be bored out and get the key slot cut. IIRC they only come in metric sizes.

I have had one now for six or seven years with no issues. I did buy replacement rubber inserts but have not had to use them. I inspect it at least yearly.