I was not offering to do the maths for you, I am sure you can manage that yourself.
I was offering to measure the actual voltage drop difference across the different types of contacts. (I have access to kit that will allow me to do that very accurately)
I was not recommending the magnet mod as such, I just mentioned that others had done that particular mod and they had experienced less arcing. Its obvious that using this mod with a damaged battery wrap would be unwise. Using a battery with a damaged wrap is not advisable in any circumstance. My personal preference is to use the recommended button top batteries.
Adding a small amount of solder to the riveted joint of the hot spring it not going to cause a problem, it just creates a better mechanical and electrical connection between the base of the spring and the mounting plate. This is one of the areas that causes a small voltage drop, as you have said the spring can move under compression and cause an inconsistent connection, the rivet is the weak point.
Its the total circuit that dictates the current draw and therefore the battery life.
My measurements on the standard grand contacts include the contact resistance.
The amount of power wasted across the contacts will vary with the current, as the coil resistance approaches the contact resistance the amount of wasted power will increase.
I've done some examples at different coil resistances to show what I mean.
The above shows the wasted power at different coil resistances, the mod volt drop is the difference between a resistance of 0.030 ohms that I measured, and zero. What ever you use instead as a positive and negative connection will have some resistance, and some contact resistance it is unavoidable.
I would guess the realistic volt drop difference between modified and unmodified would be around 0.3 to 0.4 volts when using a 0.2 ohm coil, at the maximum battery voltage. This would certainly be a noticeable difference. The difference however would be much less when using a higher ohm coil.
There is no one size fits all solution, we all have different preferences, and different attitudes to the apparent risks of using a magnet, or removing the hot spring, or low sub ohm vaping. No right and wrong just different.
Some people don't even squonk ffs.