We had the same issues (and many others) with making customized modules using the sample of Products.
What we did in the end, and helped us a lot, was to use a different approach for making custom modules where we had full control over the DAL layer and everything.
Please watch a very good movie posted by Telerik a few days ago:
It's not using the same approach as Products but you can create fully customized modules and if you use Sitefinity skin you can simulate the current SF4.1 look & feel.
For us worked like a charm.
Hope it helps!