Install older version of XVM, install mod pack. Bam, works!
If you want to merge with another XVM config, copy and replace all the files in the pack's config folder with your config you want to use EXCEPT anything that starts with the word marker. If something isn't working right, it may be incompatible with the XVM.swf file in the pack, or you are going to have to edit the individual .xc files and point to any resources that are in the wrong directory.
aidenUC, is there any chance you can find out why the pack's reloading bar isn't working with the new XVM?