Shuttle Xpress is designed to carry and deploy two small foam gliders.  In my experience, short delay motors B6-2 and C6-3 work the best to deploy gliders at apogee.

I replaced the kit's gliders (that didn't fly well) with two small foam airplane gliders I bought at Hobby Lobby that actually glide very well and cost very little to buy.

I super-glued each glider's wing and tail in place to ensure they hold tight during take-off and when the ejection charge fires.  It works.  

The challenge was adding a launch hook to each airplane glider secure enough to hold it onto the rocket during ascent, yet small enough to ensure its release when the ejection charge fires.  The hook had to be light enough not to cause the glider to nose dive.  After a few trials, I found a solution by inserting and gluing a carefully cut and shaped plastic-coated paper clip wire into the nose of each glider.  Launches appear unaffected. 

You can have some fun with this kit by experimenting with various ultra-light gliders!