I though the big problem with a silicone based dot 5 fluid was the incompatability with water - rather than the fluid taking on water (i.e., the two mixing together like a normal dot 3 or 4, causing the fluid to get dark colored and the boiling point to drop) the water tends to pool - resulting in increased corrosion, plus a portion of the hydraulic system filled with a fluid which generally becomes gaseous (i.e., steam) at brake operating temps.

I was under the impression that the Dot 5.1 fluids, which are non-silicone, addressed this issue and could be used in pretty much any brake system without fear of the silicone/water problem...

 

See:

http://www.team.net/sol/tech/dot5.html

To get info on DOT 5 fluids.