do 2 rails and carrages equal 1 hiwin for cost?
I will do a calculation to see which is the lightest ( and also the cheapest!)
This is a quick model of the Gantry I have knocked up with the SBR16 mounted on two 30 x 60 Extrusions
Looks promising!

Click image for larger version. 

Name:	Gantry.jpg 
Views:	1275 
Size:	148.4 KB 
ID:	2452

Andy