Calculate pitch balance of RC glider?
Joe Ayoob's world record throw of the John Collins designed paper airplane is worth watching over and over again.

Every time I throw the glider with my hand ...

This caused me to split my free flight hobby into throwing gliders and launching from a hill.
A thrown glider experiences a wide range of speeds in flight, therefor it cannot be set with a staticly stable &quot;tail downforce/weight forward&quot; arrangement.  This type of glider will loop if thrown hard, but will be fine if thrown off a hill.  Try to gently release it at its trim speed.  Moving the weight/changing tail decalage will produce the best glide.
But for throwing on flat ground for distance the glider must be slightly staticly unstable to keep flying as it slows down.  You want it to gradually pitch up (increasing AOA) as it loses speed to generate adequate lift for level flight.
The plane flies straight out until it stalls.  Notice on Joe's throw the glider went around 150 feet, from 40 mph to maybe 5 mph, stalled, then recovered from the dive, flying on to the world record.

Glider has asymmetric tail, which produce downforce, then glider is &quot;tail heavy&quot;

An asymmetric tail will produce pitching force aerodynamicly, not by weight.  This is why &quot;classic&quot; aircraft design has an &quot;upright&quot; vertical stabilizer (many glider designers also benefit by putting the horizontal stabilizer on top in &quot;T&quot; fashion, increasing pitch torque without adding drag).  The tail must produce a down pitching force to &quot;set&quot; wing AOA if CG is forward.
For &quot;throwing&quot; gliders, you need tail upforce, weight aft (while maintaining directional stability), and some luck to go 226 feet. If one can control the elevator (by R/C) in flight, then discus launched gliders (DLGs) are worth a look!