I think a more important aspect than float shape I've been getting wrong is plumbing up, been plumbing up to where my float was shotted, so think I've been underdepth most of the time, could be why I miss quite a lot of bites. More practice needed in that area I think before I worry about float choice
The thing about plumbing up is that it is only a guide to the depth. A silty or uneven lake bed can mean that you are off "dead depth" by some way.
Take time to plumb up and get an image in mind of how the lake bed appears. There could be a deeper part where someone has fed recently and the fish have dug out a shallow depression while rooting for food. Plumb up from bank to full depth so you understand the profile of the margin slope. On a silty lake it can pay to fish just up the slope on harder ground. You may also find shelves or sudden drop offs, both potential fish holding spots. A shelf does not need to be wide, just a couple of inches is enough.
Once you are happy that you have established the depth then hook the rig into the topkit and grasp the connector and pull some elastic from the tip. This will release the elastic's tension on the rig and you should see the float move slightly towards the butt end as the line unstretches. Mark the float's position on the topkit with a chinagraph pencil, Typp-Ex or a piece of tape. This gives you a reference point to return to if you play around with the depth.
You now have a starting point. You need to decide whether you are going to fish "dead depth" or with some line on the deck. I am guessing but I would think most anglers will look to start with 1 inch or so of line on the deck. This can be achieved by plumbing up top the bottom or middle of the float body.
If you suspect the lake bed is soft and the plummet sinking in giving a false, overdepth reading then you need to check this using something lighter as a plummet that will not sink into the silt or mud. This could be a large grain of corn or large expander pellet. Plumb up and get your indicated depth established and marked on your topkit. Then move the float down so that the rig is underdepth by a couple of inches. Now get the rig shotted and dotted down with something like a 4 mil expander on the hook. Replace the expander with a grain of corn and this should sink the float more than the pellet did. Increase depth gradually until the float is showing as it was when shotted underdepth. The grain of corn is now resting on the actual surface of the bottom mud. Mark this depth on your topkit and then add the amount you want to fish overdepth or leave it as is to fish dead depth.
Feeding fish will hollow out the area where they are feeding so regularly check the depth with a grain of corn, particularly if bites dry up.