Just letting everyone know that once I fixed the problems in the HTML includes header (all problems created by me :p) the upgrade from 7.5.6 to 7.6 went great. The upgraded forum has been running great and I've taken the time to do a few more script and theme customizations to get the desired look. Since I've changed the forum look on the upgrade with the new default 7.6.0 theme there have been compliments from some of the forum users, and nobody has reported any problems.
For those doing customization of any files, I recommend using a free open source tool called
Winmerge. It allows you to open two files side by side and easily see the changes you are making. I create a directory structure the duplicates the installed UBB.threads structure and copy the files to be modified in that structure. I rename the files to include the version number for the original file (e.g. showmembers.tpl becomes showmembers7.6.0.tpl). I then either copy a previous file if it was already modified, or duplicate the original file in the directory with the desired target name). The two files are opened, and it is easy to see any differences. By retaining the original 7.6.0 file in the directory, I can easily revert back to the original source if I really screw something up. After modifying all the files, I ftp the structure up to the server, and once everything is tested, delete from the server all the files with 7.6.0 in the name.
Thanks for the help of those who chimed in, and I hope this tip helps others.
