As a drop tank is a shape designed for minimum drag in trans, or even super, sonic airflow in clean air and your bike needs a shape that will be stable, indifferent and definitely not fly, in dirty air, at very subsonic speeds, I suggest you don't do this.

but if you must, mount it blunt end forward, fit a fin and tape a length of 5mm wire right round the nose. Try and eliminate any internal flow through the holes you mention making.

Or, more usefully, stay indoors and read some good books about vehicle aerodynamics, notng that no-one has used drop tanks as vehicle bodywork since the fifties.

maybe a glider canopy would be better. I have have decided to stay sub-sonic for now.

It's depressingly non-creative but these are the facts;-

At road speeds frontal area is the main determinant of drag. Reduce drag? Reduce frontal area, Hence FFs (not the only reason)

Given minimal frontal area, a house brick, on edge, gets you to within 80% of available efficiency.

Get most of the rest by radiussing front edges to 10% of vehicle length, Tapering rear 2/3rds. of brick at five degrees, radius rear edges (less critical).

All you need then is directional stability (a fin), Indifference to turbulence (Separation features) and an absence of any other disturbances.

Given the last point you may find providing intakes, outlets, lights, mirrors, rider access and ground clearance takes most work...

But it's really interesting, even though your efficient shape will look just like everyone elses efficient shape - it's all the same air.

my bike isn't the same as anyone else's

Of course I understand that your bike is entirely unique. This is what motivates most people to build an FF in the first place. I salute in this respect Mr. Partridge who refused to look at any other FF's in case it "Polluted the purity of his innovation". It's certainly unusual to do it in the hope of making better vehicles - which invariably involves studying all the worse vehicles and copying any better ideas.

However, the air knows nothing of this and will react, quite predictably, to any shape presented to it. It may therefor be worthwhile to obtain some understanding of that reaction...

I've always been a fan of this minimalist effort. It seems eminently buildable as a kit, if someone would provide a chassis with steering head and engine mounts attached.

Like many kit builders though I'd have my own ideas about customising it.

To improve the drag I'd reduce the frontal area by lowering the seat so that it's level with the aluminium plate, lower the engine a bit maybe and put a custom fuel tank below directly below where the tank is now, below the alloy plate. Also I'd give the seat a backrest so that the rider was less upright and move the secondary steering to suit. Ideally the chassis rake could be changed so that the highest point of the naked bike would now be the top of the steering.

That's when I'd look for one of Royce's streamlined bricks to put around it. The problem is I'd probably not have it finished by 2050.

So, well done again for getting it this far and on the road and good luck with however you proceed.