I don't know if anyone touched on this, but earlier in the thread everyone was looking for a good clear coat or casting the bottom piece in clear resin (but the air bubble issue came up) to get a super clear resin piece.
My suggestion and technique I'm going to use for a clear bottom section is an old car modelers trick.
Sand up the lower section as described here, then coat/dip with FUTURE FLOOR WAX.
This coating is what I use when making NASCAR models and want a super clear windshield. You can actually sand defects out of the the windshield, wet sand it up then "dip" the windshield into the floor wax for a crystal clear window application. Its has flawless results - and no air bubbles or runs.
I'm sure this would work with the rangefinders clear plastic bottom as described here for a super clear, bubble free finish.
If I ever get to it and do one up I'll post pics.:facepalm