letterbox shipping

hi there, I've done a lot of searching on this forum on letterbox shipping. There are several mods to enable letterbox shipping but these work (as far as I saw) with weight or size. I would like to have a checkbox in the backend where I can set products as suitable for letterbox or not and give the ammount of this product that would fit. Also a combi of two different items (both individually suitable for letterbox shipping) should be possible, for instance max. 1 of item a combined with 1 of item b. In the frontend the customer will just see that the letterbox rate is counted, he/she is not able to set anything.

can anybody help me out?

thanks in advance, Patrick

It sounds like what you want is shipping based on volume. If a letterbox had a volume of 5, then you'd know it could fit 5 of product A if it had a volume of 1, or 2 of product B if it had a volume of 2. This would also work with item combinations (e.g. 3 of Product A + 1 of Product B).

I have a Volume-Based Shipping extension that can create volume-based rates. You'd then just need to set the product dimensions correctly to determine how many would fit in a box.