Try using Testor's clear parts/window maker glue. I have used it to make "lenses" for a set of ditch lights. Turned out great! JMS
For larger areas, I would recommend doing it in layers. That way the bottom will dry clear instead of slightly milky. JMS
I have two Bowser Alco C-636's and i can pull a forty car train with ease with them. Might check how well your cars roll. Could be cars with the brakes partly set.
Well, it has taken an awfully long time for Bowser to get out the corrected versions. But THEY ARE OUT NOW!!! Note that the left-facing model linked to in post #79 is now showing the correct tank size. That is because Bowser corrected the picture in their web site the post linked to. So for the moment at least one gets a fine comparison of the correct tank and the tank that is too small.