1. PHP REQUIREMENT LINK : https://github.com/flatpressblog/flatpress
2. We offer incremental upgrade i.e for example 1.1 to 1.2 but not from previous versions to 1.2 as vendor provides upgrade zip for upgrading incremental versions. change minimum required version in <min_require> tag in info.xml and make relevant changes in upgrade.php in every update. Download upgrade package from here https://www.flatpress.org/download
3. We have explicitely added "en-us" in settings-defaults.php file before starting curl_call because the installer takes "cs-cz" only despite of adding en-us in the post parameter. (Check in next version)(Checked in 1.5.1 not required, hence removed)
4. Ignore the .git and .github folders while making our zip. (If any)
5. We have made a manual change in fp-includes/core/core.utils.php file to make it work on PHP 7.1 since 1.4 upgrade as suggested by vendor.
https://github.com/flatpressblog/flatpress/issues/630(not needed since 1.4.1)
6. Upgrade documentation: https://www.flatpress.org/download
7. Always check in upgrade, if setup location is required or not in upgrade.xml and handle accordingly. It wasn't required for 1.4.x to 1.5.1 as mentioned in the link  https://wiki.flatpress.org/en:doc:basic:upgrade