Pistol Scopes

Myself I do not use pistol scope on my pistols. The two I bought was mounted and used a couple of times, but the "straight arm shooting " isn't for me I suppose. I use light airgun scopes, combined with a laser, or I go for a redpoint. With these I can rest the pistol in the hook of my left arm, and have a firm base/rest. 
With the laser you just aim, holding the gun firmly to your body, but in bright daylight the laser is no good, so you have to have an optional sight. For the Weirauch hw 45 I use a see through mount for the laser, and therefore I can use the iron sights when it is not conditions for the laser.
for the FX Ranchero I use a short riflescope (sun opticks), and a laser mounted underneath the scope, which allows me to use both options at the same time if I wish. (Waiting for the new Athlon to replace the Sun opticks - another thread here....)
For the RWS magnum I use only a red point sight.
And of course I have pistols with their original iron sights, which is challenging to shoot with - but to my understanding the Rex do not have sights, just the rail base?

 
I recently installed a reflex on my Prod which proved to be more accurate than the centerpoint it replaced. It was great to knock down targets out to 20yds but soon missed the power of a scope. So I got a UTG 3-9x32 Bug Buster. The compact size of this scope is a perfect match for the Prod and probably most pistols include the Rex. All depend if you plan on holding it like a pistol or somehow get a stock on the Rex to shoulder.