Try not to add any solder as it increases the weight of the float.
I've put several good floats in petrol to see how high they float. I've done the same with a few repaired ones, some I did, some others had done.
All the repaired ones floated low and some even had one float sink.
It doesn't take much to change the floating height. I chased float level problems for a few months till I worked out what was happening.