Additional Shipping Fees

Hello I’m trying to add a set additional item fee for each shipping type, e.g. flat rate. Let’s say the flat rate is $7.50 and I’d like to add $1.50 or “any price” as an additional standard fee. I tried to follow your documentation but it was confusing. I added the additional fee under flat rate shipping class cost: 1.50 [fee]. So basically with the above information 2 items would ship for $9. Can you tell me if that is correct or provide the correct steps to make the desired change.

Thank you!

My site is: alinefabrics.com btw