Shipping Calculator - Built In v. Addon v. Custom - What to use?

I am planning to go live with my zen-cart site this year.
The site will carry several thousand items of various sizes and weights.
I am struggling to figure out which direction I should go - using the existing Shipping Modules, going with an Addon, or creating my own custom module.
The existing modules are limited at best. Because we sell so many items and they do not fall into a small set of shipping sizes/weights, I am worried about using the existing modules and either losing money in the shipping aspect or losing customers in the approach.
We are not trying to make money - just break even.
I've looked at add-on modules like auctioninc.com and shippingcalc.com. I am concerned about whether the product will continue to be supported. It doesn't look like they have support for version 1.55. I have no idea how many people even use these add-ons, which would help me understand if the support would continue.
While I could create a custom module, i am concerned about the maintenance and effort. If I knew the add-on would work and be supported, I would likely go that route. I know I can create the custom php code and build a pretty complex database set of rules and stored procedures to calculate information accurately, but again ... my time is important. I have no idea how often rates change for shipping so that in itself may become overwhelming.
I see a lot of posts about specific issues, but not much about information regarding the use of Add-ons.
My ranking would be 1) Add-ons 2) Custom 3) Delivered zen-cart modules.
If anyone has information or can share a current experience with an Add-on vendor, that would be great.

Get Advanced Shipper
http://ceon.net/
You can do almost anything with this. And if you can't, it's a very well-written code is the best base you will find.
No I have no connection with them.

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Originally Posted by torvista

Get Advanced Shipper
http://ceon.net/
You can do almost anything with this. And if you can't, it's a very well-written code is the best base you will find.

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I second that!

Quote:

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Originally Posted by torvista

Get Advanced Shipper
http://ceon.net/
You can do almost anything with this. And if you can't, it's a very well-written code is the best base you will find.
No I have no connection with them.

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I appreciate the feedback. I reviewed their site and read about all 3 of their products.
What I could not find was anything related to dimensions. Everything is focused on weight.
Unfortunately I cannot always pack a box based on weight. I need to know the size a product is in order to put it in a box with other items.
And I am collecting dimensions for every product as well as weight. I just don't see anything from ceon that talks about how to pack a box based on dimensions.
True, each box has a dimensional weight limit and anything above that becomes super expensive to ship so I do need to take that into account.
But if I have 10 items to ship and 6 different box sizes, I need the application to help me decide how to pack the items so I can pass on the most accurate shipping cost to the customer.
I found the following https://github.com/dvdoug/BoxPacker on the web and may try seeing how to implement the code into a custom zen-cart module.
If not, then I may end up returning to ceon.

Thanks for the feedback and looking forward to any additional comments.

You might want to look at the weight differently. If an item actually weighs less than it's dimensional weight, the lesser weight is irrelevant. As the pdf at http://tinyurl.com/n675lju shows, a 1 pound pillow takes up more "space" than a 1 pound pair of shoes.
We may need to start reevaluating all our weights to dimensional versus actual weight. Included in the pdf is a table for calculating such weight.
We have one customer that takes advantage of the USPS regional boxes. Provided free and cheaper than other rates when used regionally.

I use the regional boxes almost exclusively. Most of our products will fit well in the Regional Rate A boxes. The only thing to watch out for is that they really are "regional" rates. For locations within 100 miles of your shipping origination, the regular Priority rate is often less (though usually not more than a few cents less). For locations on the opposite coast, medium and large flat rate boxes may be cheaper. We just enable all the choices and let the customer pick which one they want. Since the customer is normally going to choose the least expensive option, all we have to do is make sure we don't have items or combinations of items that can't be shipped in the most likely option for the customer to choose (like a bulky item in a small flat rate box, for example). We have heavily customized the USPS shipping module to exclude the choices that would cost us the most money if the customer picked those.