In my humble opinion, neither "fuller" nor "More full" seems to be correct, because FULL is a absolute concept. Words such as complete, perfect, and full can not be sensibly compared. Something is either full or not. There are no higher things of fullness. :)
However, adverbs can help you to make a great comparisons.
As always, English is surprising us with EXCEPTIONS :)
In Cambridge Grammar of English book, I saw the following phrase at the bottom of the page " For fuller discussion of SOME and ANY".
The authors were talking about the usage of the words such as some and any; then they wanted to say that for more information regarding this subject, go page xxxxx..
Below is the snapshot.