Derived parts with mate connectors...

So, I have been playing with Onshape and trying to figure out how I can use existing parts in a parts studio to possibly create a piping module with contextual relationships, etc.  I found the webinar on derived parts and thought it might be a promising solution to this problem.  Using 3DX certified pipe fittings, I added mate connectors on all of the possible connection points on the fitting.  I inserted the derived part into my parts studio, and used the transform by mate connector tool.... it works pretty good, with one exception, and it's kind of a big one. The only mate connector that follows the part with the transform is the one you use, (which might not be a huge deal, as I am able to add additional mate connectors to the derived part if I need to, however it leaves the others behind and you can't delete them without deleting the derived part.  If you transform the part in other ways first, all of the mate connectors are left behind.  A solution to this might be to only put one connector on the part, however with fittings like a tee or a reducer, you would want the option to pick one connection mate over the other.  Is this a glitch or am I doing something wrong?