As mentioned, I am using two storm water end caps for the physical turrent. The first test just eyeballed the centres however I now need to get a better version. The caps I have have a 11cm inside diameter (with a lip about 2cm high).

To get a decent template, I fired up Visio, drew a 11cm circle then placed two lines thru the centre (one vertical and one horizontal). The ends of these lines give me the LIDAR centre positions. At the centre of the 11cm circle I put a little tiny circle - this is a drill guide spot.

Printed it out and made work with the scissors and dropped it into one of the end-caps. Fitted perfectly so now have the drill template and the exact positioning for each lidar.