Well, really, the problem is that, if you are using an aluminum tank and minimal exposure protection, and then you hang those heavy fins off the ends of your legs, the fins have a very long
lever to affect the position in which you are stable, when you are not moving (known as "trim"). Wearing heavy fins in that circumstance, especially if you are using a long-leg kick (rather than the knee-bent kicks that the cave divers use) is going to obligate you to be feet-down. Being feet down has several bad consequences . . . for one thing, you kick stuff, and you kick up the bottom, which is not at all nice in lakes or anyplace else that's silty. For another thing, if your feet are aimed down, each time you kick, you go -- UP! So you have to keep yourself negative, to avoid climbing in the water column, which means you're spending a lot of energy going nowhere, and worse, if you stop kicking, you sink.
You can ameliorate the effect with posture. Bending your knees shortens the lever, and putting your arms out in front of you gives you a bit of counterbalance. I can dive my size L Jets (which are similar to F1s, only smaller) in warm water without tilting feet-down, but I have a lot of experience in using my body as a balancer. AND my fins are smaller, and therefore less negative than F1s.
I think a similar fin would be a great choice, but I'd go with the OMS Slipstreams or the Dive Rites, which are much less negative. You'll still have a nice paddle fin that will let you move on to any kind of diving you want to do, but you won't have the diving equivalent of concrete overshoes