Which clamps on the market fit circle 10 magazines? Would this one fit?
The item pictured looks to be intended for steel magazines with the raised narrow spine. Circle 10's have a low rounded spine. You might look at one like the CAA
version with triangle cutout.
I don't have experience with them and personally I wouldn't buy them either. Loaded AK mags weigh enough as is, let alone two loaded AK magazines.
If you want to carry more magazines with you, invest in a magazine chest rig like the Chicom chest rig