Anything will have less drag than what you have
Like I said you provide a design of your ideal system and I will tell you why it will not perform as well.
, even wrapping tape over the bolts and edges will slightly decrease the drag. The easiest would be to fabricate a streamlined fiberglass fairing to cover the whole mess, right up to the prop. It would even help with the weeds a little.
So you would not change anything other than a little bit of cosmetic detail to fair over the 4mm nuts? Something like this:
A lot of effort for no measurable performance but it looks cleaner so more commercial appeal.
But don't listen to me, or the designer of the Vesta or Savitksy, none of us know anything.