The original navcore is much smaller then 70Mb.
Then you have to look for a map that is compatible whit this navcore.
You also can try to delete the file poi.dat from the RBF mapfolder and look if it wil fit then in the availiable storage.
If necessary also delete:
-Cspeech files from mapfolder, you don't need them for TomTom one.
-Unnecessary voices from Voice folder
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