Hi Gerhad (OE3BGA),
It's nice to see another HAM here at Laptop GPS World. I've myself spent the best years of my life (some 20 years ago) operating under various OK3 call signs (that would now be OM). I've even briefly went on the air once as /OE from your homeland. Now I'm licensed as VE3VEE, but I have no space for any serious antennas, and I haven't been much active from this part of the world at all.
But to your questions... I agree with your assumption that since the mount has been designed for laptop computers, your TCVR, which is lighter than most laptops should be safe.
I'm not sure about the flex arm question, but here's a link to the catalogs:
RAM Mounting Systems, Inc. > Support Center > Catalogs -- and if our friend Ram_Mount_Expert stumbles upon this thread, he may offer you his insight.
73