Tankless water heater Rinnai R98LSi QUESTION
If you are using the meter in the sizing of gas pipe and then subtracting a percentage for pipe length then I will say you need to learn how to size gas pipe, because the way you are sizing pipe is all wrong.
A meter being under sized is no big deal once you properly size the pipe for the appliances served. Just a simple call to the utility company stating that the meter is to small and they will change it out.
I would also caution you that if you are not a licensed and qualified contractor installing water heaters some and most code jurisdictions frown on this. Plus I hope that you are carrying general liability insurance because when something goes wrong it's all about the attorney's and insurance.
John Wayne once said "Life is tough and it is even tougher if you are stupid"
Tempstar and Trane Dealer