Getting these things trimmed to glide is challenging.  At best, they tend to glide poorly.  The builder must take care to build them light, or even further challenge is added to get them to fly.  A nose down, death dive is a common landing.

With this kit, I found two things to change, one of which is critical.  The launch lug is mounted in the belly scoop, at an angle to the motor tube.  This results in it climbing the rod in a sort of crab fashion.  It straightens up as soon as it clears the rod, so the upward flight is not affected, but, with the lug that far aft and off axis, it tends to bind a little on the rod.

This can be addressed by using an internal lug, mounted along the motor tube.  A hole is added to the shroud, in the front, below the nosecone.  The only problem with this is that it adds front weight to the rocket – exactly the place you don't want more weight. 

Maybe on my next one, I'll just put a hole in the shroud, but keep the lug short and moved aft as far as possible.

Here's a liftoff shot of the HL-20 on one of its many flights.  (Photo courtesy of Tim Sapp)

The other issue I had with this kit, which is critcal, is that the forward bulkhead, between the nosecone aft and motor tube forward, is too thin.  It was basically card stock, and the first ejection event blew thru the paper and parted the nosecone

I re-engineered it with a more substantial bulkhead - one which can readily handle ejection charges - but again it adds weight where it's not wanted.

One minor issue I had was the black cockpit paint job on the card art (as shown above).  That's too tedious for someone hamfisted like myself, so I elected to leave mine unpainted (white).