Used the level to measure roll bar height from side longerons after realizing my original measurements were from the middle F605 bulkhead and that bulkhead is slightly lower than the longerons because its mounter underneath the longerons. I guess I could have compensated by adding that difference to 17 7/8, but what the heck, just measure from the longerons. Each side measured exactly right which means by luck I clamped the level onto the roll bar top correctly. If it had been tilted slightly I would have just added the two side measurements together, divided by two and hopefully would have achieved 17 7/8. Finished cleaning up and will now locate and drill the eight outside holes in the roll bar. Four of them will be tapped for #8 flush AN509 screws which will hold the upper fuselage skin onto the roll bar. The other four are flush mounted #10 AN509 screws, washers and nuts to further strengthen the roll bar and will be hidden by the fuselage skin after attaching that later.
How I eventually checked overall height to longerons.
