VERY bad idea. At 5.5PH your solo variance would be astronomical.
You firstly currently would average more than 60 days before you find a block (though the next diff change will be over 10% so it will be longer and include many more diff changes).
And if you hit over a 200% block (which is expected 1 in 7.4 blocks) that'll be more than a 1/3 of a year away, with no income until you find a block.
5.5PH is not big time - it's quite small compared to the bitcoin network which is currently over 47976PH.
I stand corrected. But as a gambling, it would work.
But why do you think the next diff change will be over 10%?? When I look at the trend: Shouldn't it go rather a bit down?