handling fees to cover shipping insurance, fuel surcharges etc from Fed Ex

[STOPit]

I see I can add a handling charge to the shipping costs. I would like to do that to cover shipping insurance, fuel surcharges etc that Fed Ex charges after the fact. Would I add a % to the shipping rate. So if my rate has a 45% discount from Fed Ex and Shopify uses my account rate to quote shipping costs. Would I then put in a rate adjustment of 182% to get back to full street shipping rates? Published street cost of $100. discounted by 45% make my rate $55. if I add 182% to my rate this would make new cost to customer $100.10. Am I doing this correctly?