I am trying to find out if there is a way to charge a different postage fee for specific products.
For example; I sell stencils on my website. Some of the stencils are large and postage starts at $3.50 for first class through USPS and the amount goes up after 8 stencils to $6.50 and so on.
However, I have these little stencils that are small enough to fit in a letter size envelope. If a customer orders 1 of these little 2.5x9 stencils that fit in an envelope for a whopping 48¢, I don't want them to have to pay $3.50 in shipping fees.
What I would like to be able to offer is 1-5 stencils ship for $1.50, 6-10 stencils ship for $2.50 and 11 and up get to fall into the $3.50 and up shipping, BUT ONLY FOR THESE SPECIFIC little stencils. Also, if they mix the little stencils and order big stencils with it, the option of that envelope size shipping fee is no longer an option.
I had set up shipping so that when they checked out they would have the option of $1.50 shipping but too many times customer order big stencils would choose that shipping rate even though it said “Letter Size Envelope max size 4x9”. I was having to call the customers and get them to pay the remaining postage fees and of course that means more fees for credit card processing.
I had to remove that shipping option and now my customers that are ordering these little stencils are stuck paying the $3.50 fee. I was trying to refund them all the difference but that is sooooo time consuming. I don't do that at all anymore and just ship them in a small box.
Assuming you have weight of products set for every product, you can do Like you did before but add a weight limit allowance in the delivery option on the .48c postage and use weight modifiers if nneds be…
So if your “1” small stencil weighs 25g set your weight to say 50g so they can order 2 then after 2 that delivery option wont show above 50g.
Then you will have the other weight option for heavier items set to charge more
JOhn
Thank you John…I was afraid that might be my only option 
I have over 4,000 products so I am dreading it lol…but I think you are right and I shall give it a shot. I appreciate you taking the time to help me out.
Not so bad to import all the weights if you dont already have them set up.
What I did was export the product code and product option for each product, then I did a find and replace in excel for say “size a” and replaced that with the corresponding weight of say"20g" then the same with “size b” = “50g” etc etc
Then changed the column title to weight and imported back in just code and weight.
the killer is if you have hundreds of individual sizes, and not say just dozens of groups, check out the “text to columns” feature in excel