I have a welter duel exhaust and I very rarely smell fumes.
I don't think type/size windshield has much to do with it.
I think the reason is the way my roof is designed.
The same thing that sucked out the dead red bird removes the fume.
The large gap acts like a chimney.
I’ve used double bubbles and a straight windshield.
Roofs Curved downward in the back forces air to swirl toward the cockpit
My straight roof with the big gap forces air upwards and away from the cockpit.
Result.... no fumes to smell
Put it in a wind tunnel and see, the flat could cause a roll after leaving. It might be the plastic wind stop you have on it that is helping you.
With my short straight windshield or my double bubbles I have a large amount of wind going under and over the roof. The wind coming in under the roof is being forced to exit through a smaller opening than it has coming in. I think that negates the roll coming back in to the cockpit.
A roof with a rear downward tilt is probably adding to the toll of the wind being forced into the cockpit from the rear.
If your windshield is allowing air to go under your top and you have the windrestrictor in the back, then your cockpit area would be higher pressure than the area behind the windrestrictor. In that situation, the air would push through those openings preventing the exhaust fumes from moving forward and into the cockpit.
Where we see the most issues with fumes is when the air goes up and over the tops, especially with no windrestrictor, as this creates a lower pressure area in the cockpit and fumes move forward from the back of the Slingshot to fill that low pressure area.
aerodynamics around a complex shape like a slingshot (with or without a top) are really complex. I've seen wind tunnel and real life testing with short strips of ribbon taped to the surfaces and edges.
Be interesting to see outboard camera footage of ribbons to see what these look like as you adjust wind screens, spoilers, wing, etc.
aerodynamics around a complex shape like a slingshot (with or without a top) are really complex. I've seen wind tunnel and real life testing with short strips of ribbon taped to the surfaces and edges.
Be interesting to see outboard camera footage of ribbons to see what these look like as you adjust wind screens, spoilers, wing, etc.
Have you ever rode behind a Slingshot with flags on the back plate holder and see which direction the flag flies?
Have you ever rode behind a Slingshot with flags on the back plate holder and see which direction the flag flies?
No. The only sling I've ridden behind was dangerdarrell, and there was no way I was keeping up with his supercharged sling!
This would be a fun experiment though!
The flags fly sideways or backwards, so the fumes go right back into the cockpit because of the dead air space behind the wind screen
I have two flags on the back and they aren’t flapping around like you think they should be.
How do your local law enforcement allow that rear license plate? 
How do your local law enforcement allow that rear license plate?
They don’t.... I’m an outlaw, rebel without a cause, hell on wheels, a devil may care, hell’s angel, a punisher....screw the man....I don’t care nothin about what John Law thinks...
They don’t.... I’m an outlaw, rebel without a cause, hell on wheels, a devil may care, hell’s angel, a punisher....screw the man....I don’t care nothin about what John Law thinks...
Until the lights go on behind you? 😂
It’s actually worse than that 
🙋♂️
