Thanks @EatThePath, that is helpful advice! The current fins are tapered in all directions, but it probably needs to be more pronounced. As @Pouk pointed out before, the bevel in the middle is cheap and needs sorting. If only the HWRM folks had been listening to your advice, maybe they would have done a better job of this Hiigaran corvette’s rear fin:

On the other hand I do like this (especially the lights), even though it doesn’t have pronounced taper:








