Remember that LRPL 2018 average is 91. Guppy would never do that.
No reason why they can't bat for longer, it depends what they can get out of the T20 player leagues.
Big grounds mean big 6's, it also means losing wickets. Remember this is Sri Lanka, a currently lowly team, on our tracks. It's a long way from ICC WC in the UK. Wait till India has been here. Thats where we will see if the No.3 ranking is real.