Sleepers for aluminium or wood rails

This is Sleepers you can use outdoor with aluminium or wood rails (still testing with wood).
I have noticed that the rails on my old designs are sagging a little if it is to hot in the sun or if you are using live steam loco. The aluminium flat bar i am using in the pictures are 3 x 15 mm.
If you have other sizes you want to use i can make sleepers fitting these.
My next big release will be a bigger loco than my old one, but because my old 3d design software stopped working i lost around 60%