So, thought I'd try out the configuration of the Heartseeker on my current F7C-M.. I'll admit it took a bit of flying other jobs to get enough money to buy 3 M5's (pulled an M6 off my Connie and I still have a Flash mount in my hangar). That in itself is almost worth the variant so I don't have to gather the credits to buy the guns. However, I put it altogether, went and ran some bounty hunter jobs--find and destroy.
The weapon combo of 3x M5's and 1x M6 does great, kills fast, and a lot of damage, but holy smokes does it fire SLOW!!!
In the end, I still think I'm going to stay to my stock F7C-M. The stock configuration comes with not only the ball turret but the canard turret too all loaded with faster firing weapons. I'd lose those if I applied a Heartseeker variant CCU. I also really liked the faster-firing weapons for my preferred play-style. If I ever want the 4 slow firing lasers loadout again, I can always acquire them in-game.