I have been looking everywhere to find wood stripes, to slide in my lcd and fresnels. The stripes i have found are 20mm wide, which will be fine to place between the collector fresnel and lcd. Now the collimator fresnel needs to be 15mm from the lcd. If i was to use a 20mm stripe between the collimator and the lcd, will this be ok or not?

Thanks guys.

yes it should be just fine, being collimated the light will not diverge (or at least not enough to matter) especially in 5 mm....

edit...the only real difference will be that the air volume between the lcd and collimating fresnel will be greater but I can't see that making much difference either(assuming you're using standard LL setup..)

Thanks mate. I will leave 20mm on both sides.