It works the same way for everybody. It makes a difference whether you put the weight on the top bolt or the bottom bolt or somewhere else. With enough experience, you will be able to tolerate these differences better; you learn how to move you arms, your legs and your head in different ways to counteract being head heavy or leg heavy.
When I first started diving doubles, I had my rig set up such that the tanks were very high up on my back. My valves were almost at the same level as my ears. It made for an easy reach of my valves but it also made for very head heavy trim. My fundies instructor made my life 100x easier by showing me that my rig needed to be lower down my back. One way to accomplish this is simply tightening the crotch strap. Sometimes, this is insufficient and an adjustment of the shoulder straps are necessary.
In my case, I moved my rig as far "south" as I could. By this I mean, I can still do a valve drill with my drysuit and heavy UGs on. By moving my rig as far south as I could, I was able to get some flexibility as to where to put weights. Specifically, I am now able to put weights in the middle of the rig instead of hanging all my weights on the bottom bolt.
So the short of it is, do you have your rig adjusted so it is as far south as it needs to be?
Finally, instead of using cave line to tie weights to your bottom bolt, there are a couple of other solutions which I think are better. First, Deep Sea Supply sells weight pouches which can be attached to the bottom bolt of your doubles. This is good for about 5lbs of soft weights. Second is what I have personally done. I cut a v-weight to a size that would fit from the bottom of the bottom band to the bottom of the tanks. On my tanks, this is about 3.5" segment. I took a 4" piece of webbing and screwed it onto the flat side of the weight. I then took the strap and burn a hole in it. I secure the v-weight to the bottom bolt using the webbing. See below:
