Update BurntimeCalc 2.0: Select user engines.

[atomicdryad]

If you're unable to select the engine you want in a custom dll ship, this may resolve the issue: http://orbiterfixes.googlecode.com/svn/trunk/burntimecalc2.0/Modules/Plugin/BTC2.0.dll

The summary of changes made is here, as well as the full source code: http://code.google.com/p/orbiterfixes/source/detail?r=13