Shipping quotes with mixed content types question

I have a site with two shippable product types: T-Shirts and Bumper Stickers. I have set up flat rate shipping amounts for varying quantities as follows:

Envelope (10 stickers or less)
$1.00 + $0.02 per item

Envelope (11-50 stickers)
$2.50 + $0.02 per item

Envelope (51-100 stickers)
$4.50 + $0.01 per item

Small Package (101-500 stickers)
$7.00 + $0.01 per item

Package (501-1000 stickers)
$8.00 + $0.01 per item

Large Package (over 1000 stickers)
$9.00 + $0.01 per item

Envelope (1-2 shirts)
$0.00 + $2.50 per item

Package (3-12 shirts)
$5.00 + $1.00 per item

Large Package (over 12 shirts)
$12.00 + $0.50 per item

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Then I set up conditions on each shipping method similar to this one for 3-12 shirts:

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Check an order's product classes
Parameter: Order: [order], Product Classes: T-Shirt, Require all selected product classes: false, Forbid other product classes: false

Check an order's number of products
Parameter: Order: [order], Products: 2000, 2079, 2080, 2085, Product count value: 3, Operator: Total is greater than or equal to 3

Check an order's number of products
Parameter: Order: [order], Products: 2000, 2079, 2080, 2085, Product count value: 12, Operator: Total is less than or equal to 12

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So long as the customer chooses ONLY Bumper Stickers or ONLY T-shirts to buy in their order, this works flawlessly. But if the customer purchases some Bumper Stickers AND some T-shirts, the shipping isn't working properly as I currently have it set up.

When I set the Conditions to Forbid other classes and an order is in the cart with BOTH Bumper Stickers and T-shirts, no shipping quote is obtainable because other classes are present in the order and so the Conditions are not being met for any of them.

When I set the Conditions to not Forbid other classes, then the shipping quote for Bumper Stickers comes up and the shipping quote for T-shirts comes up, but the quantities for the Product count value are thrown together. This results in an astronomically high shipping quote for the T-shirts if someone orders a lot of Bumper Stickers. The shipping method is set to add $2.50 for each T-shirt in the order. But when I tested what happens when someone orders 75 stickers AND 1 T-shirt, the quote used a quantity of 76 for the shirt which resulted in a $190.00 shipping charge for that one item. I'm not seeing a condition parameter for just doing a count of the specified products. The condition parameter is for counting the order's total number of products, which is causing the issue I'm having.

I know this is something where I'm just not seeing the right setting somewhere. Can you please advise how I attain the desired result?

Do I not need the Condition that checks an order's product classes? I set that up first because I didn't know that the products would be selectable within the Conditions for the order's number of products.

Thanks in advance for any help anyone can give with this.