[Morris]

The LeMans type of cap has a tendacy to leak when going around corners.....

Especially if you put the car on a track......

The other issue is filling the fuel cell quickly ...... so you put the cap in below the LeMans cap...... and then use the space between the caps as the vent area...... and drill some holes in the sealing plate of the LeMans cap to vent the fuel system thru the LeMans cap............No leaks

Also..... when you are filling the fuel cell .... the vents will start spitting at you when you are almost full..... and they just spit back into the fuel fill hole....

Morris