I meant to add,...Instead of building a second trainer like the one you already have I'd shoot for a Sig 4*. You can probably frame it up in a weekend or two, granted it's not going to advance any building skills, but it makes an 'excellent' second plane/first low wing.

Edit: The Goldberg Tiger 2/Tiger 60 are equivalent to the Sig 4*. If the Tigers are more aesthetically pleasing to you, those also make excellent second planes/first low wing. The Tiger's may offer a bit more challange then the Sigs when it comes to building...but only a bit