We have also tried with a good developer but had to abort the upgrade due to many existing functions missing and we did not have the install guide/history/files for all the features added.
I would like the developer to use the old files and add the new file content to it, he did the other way round probably .
Would appreciate some suggestions for our developers who too find this task very difficult.
Shortcuts aren't and adapters don't. I'm sure I can think of others but those two come to mind immediately.

I would recommend you use the link you posted to upgrade. And, as to functionality, the following:
  1. Many (maybe even all) of the add-ons you used in 1.3.9f are not going to work with the new files, the required PHP version, or both.
  2. Review the Plug-Ins portion of this site to see if any of the things you were using in 1.3.9f are now working in 1.5.4. Don't be skimpy in your research. Look at every item under each category to see:


  • If you used it before
  • If you need it now
  • If it's compatible with 1.5.4


If you need other customization(s) for operation of the cart, you will need to find a developer capable of the coding.

Make sure you select a responsive template for use as it WILL be needed.

When doing this method, I bloat an update directory/site temporarily with database/site backups at each step. That way, if a mod breaks the operation or gives me a blank screen, I can easily back up to the last working version.

Hardest thing to do during this process is to avoid the glitter. Remember that the need is to provide you customer(s) with a place to shop. Leave the pretty till after they can log in, shop, and purchase.