> Would an export into some other file format out of MoI and then back into MoI help
> to make an IGES more workable? Or performing various joins after the model is imported
> and then saving it out as 3dm?

If you just save the file out to 3DM format, that should then solve the "slow loading" part of the problem, but you still may have other problems to work on after that, like needing to select just specific groups of surfaces and then using Join rather than letting the whole file be processed for joining all together.

Basically you should only use IGES format just for the initial first load of the data into MoI, once you want to continue working on the file don't save it back to IGES format after that, use 3DM format for your in progress stuff.

- Michael