[Fixed] LocalHomepage not working

Using the most recent version (v61).
Fresh install -- no old Data or profiles
Created a FirefoxPortable.ini file with the following content:

[FirefoxPortable]
FirefoxDirectory=App\firefox
ProfileDirectory=Data\profile
SettingsDirectory=Data\settings
PluginsDirectory=Data\plugins
FirefoxExecutable=firefox.exe
AdditionalParameters=
LocalHomepage=
WaitForFirefox=false
DisableSplashScreen=false
AllowMultipleInstances=false
DisableIntelligentStart=false
SkipCompregFix=false
RunLocally=false
AlwaysUse32Bit=false

Set LocalHomepage to a file that came with the directory: LocalHomepage=help.html
Ran FirefoxPortable.exe -- no luck.

Took a look at the generate profiles
Went looking in prefs.js
Found no entry for a homepage
Realize there's a invalidprefs.js
Last line: user_pref("browser.startup.homepage", "file:///C:\Users\mike\Downloads\FirefoxPortable/help.html");
???
Fix the typos: user_pref("browser.startup.homepage","file://C:/Users/mike/Downloads/FirefoxPortable/help.html");
Add to prefs.js
It works.

Trace issue to FirefoxPortableU.nsi
Realize this is an issue with folder syntax.
I am running on Windows.

Issue: I still need it to work dynamically -- i.e. would rather not have to manually correct it every time I use it on a different computer
Perhaps someone here has already encountered this issue, and being much more knowledgable in writing .nsi could suggest a proper fix?