vhf antenna installation on raked masts

[Cute Helles]

I believe that all Wharram designs have raked masts of about 7 - 12 degrees in the different designs.

I wonder whether those who installed antennas in the mast top compensated for their mast rake, and whether there is any experience whether the installation in a strictly vertical position (deviating back from the mast rake) increased performance in either VHF or AIS.

From theory it seems obvious it should increase performance, even more if someone using higher gain antennas (e.g. 4.5 or 6 dbi as opposed to 3 dbi.

The two Wharrams I  bought in the last 10 years both had the antennas following the mast rake, i.e. not strictly vertical. Whilst the first boat had only VHF, I did never try to estimate how performant this was. The second boat had VHF/AIS combined with a splitter, The AIS VSWR was always to high (3:1), so probably transmitting was not very effective.

I wonder whether this was (partly) caused by the antenna position?

Any experience or ideas around?