Hi David, Thanks for your patience in a response - I have been traveling for work and am now getting settled back in.
1) SketchUp modeling techniques...
You have to build in solid geometry. SketchUp is very permissive when it comes to 'paper modeling' - faces representing walls, stray edges, missing faces, etc... You would do best to model as volumetrically as possible. If you do not work with volumes then you'll most likely have 'watertight issues' that will cause an eventual import to Revit to fail!
Try to use components / groups to have discreet building 'objects' instead of a big mass of faces and edges.
You should experiment with the way sketchup windows 'cut components' come into FormIt. I don't recall off the top of my head - but I believe the 'cut' behavior is lost, so you'd need to actually remove the opening geometry in FormIt
2) A360 generated RVT files...
I would steer you away from the 'automatically generated' RVT that appears in A360. I find the Revit add-in is a MUCH more immediate, and satisfying experience. You can choose your own Revit template file, or whether you want to import FormIt geometry into an already existing RVT project. You can work with smaller FormIt files (as recommended in previous posts) when you import, then watch progress occur, and see right away if geometry fails.
3) Pertinent to both 1 and 2 above - you should get used to using Display Watertight and Display Backfaces (DW and DB keyboard shortcuts in FormIt) as these will reveal the most common geometric fidelity issues that result from SKP imports and Revit conversion failures.
4) In Revit 2018 you will see vastly improved import behavior. So if you're not seeing FormIt geometry import to Revit today - you will see improvements soon.
Thanks, Hope this post was useful,
Tobias