Ceiling rail hardware for 80x16 rails in VW Transporter T6.1

I wanted to install some ceiling rails in my VW Transporter T6.1 so designed some models to assist with that (mostly so I can slide my surfboard into it, other model here). 

I drilled 4 x 6mm holes in the top of the rails to match the existing holes in the van ceiling. I wanted the bolts to be recessed so also drilled 19mm holes so that the bolts don't protrude above the rail.   

I created some spacers (33mm tall) to allow the straight rail to be mounted to the curved ceiling.

Bare cut aluminium doesn't look great so I created some end caps that clip on the end and are easily removable. I also created some 19mm caps for the drill holes. 

I used the following hardware: 

• 3m rail with 2 T-slots (80x16 profile) cut into lengths of 1040mm. Source: https://uk.rs-online.com/web/p/tubing-and-profile-struts/1873279. 
• M6 rivnuts (I had to widen the existing holes in the ceiling panel slightly using an 8mm drill bit, then used primer to ensure the bare metal doesn't rust)
• 4 x 25mm M6 hex socket bolts for the rail ends   
• 4 x 60mm M6 hex socket bolts for the rail centers   

On printing the end caps: I used Orca Slicer's Tree Slim supports just so that the end clips have a bit of flex in them (see build plate screenshot).