Roger,
I can start out with some good news, I've never heard of Little Helper. While it is a relatively young extension, I do not recall any support tickets or discussions about it causing problems with Admin Tools.
That said, the two will almost certainly trip over one another when modifying the .htaccess file. Admin Tools backs up the existing file and replaces it completely with a file generated from the options entered on the .htaccess Maker configuration screen. So if you use Little Helper first, Admin Tools will wipe out those changes. You may be able to use Little Helper last, if it adds lines to the .htaccess file instead of replacing it.
You should keep a copy of Joomla!'s standard .htaccess file handy to fall back on in case the two of them create a combination that doesn't work. If you need to disable Admin Tools' Web Application Firewall, the instructions are here:
https://www.akeebabackup.com/documentation/troubleshooter/atwafissues.html.
Dale L. Brackin
Support Specialist
English: native
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