Increase Shipping Cost for Larger Items

Ok, here's my situation.

I have two types of shipping scenarios. A flat rate of $7.95 that is charged on all orders under $100, and most orders over $100 are free.

We also have products that are "oversized" and need to have shipping charges regardless of the order value. The shipping charge of these oversized items needs to be calculated by taking the $7.95 flat rate and adding 20% of the item value for every additional unit purchased.

Example:
If an item cost $10.00, then the shipping charge for a quantity of 1 would be 7.95 + 10.00 x .2 = 9.95. The shipping charge for a quantity of 2 would be 9.95 + 10.00 x .2 = 11.95. And this would continue for each additional unit purchased.

Our current solution makes the free shipping option into an "And" statement so that orders over $100, but less than a certain weight are free. Anything over that weight goes to the Table Rate. The problem is the table rate only allows for percentages of the order total, and that doesn't work for us.

Anybody know if this is possible? Help would be greatly appreciated.

Thanks