Sony Flip 15 upgrade

I have a SONY Flip 15 convertible tablet (SVF15N17CXB) that I use primarily for contract work that requires a PC.  It is a very nice machine with an i7, 8G of RAM and switching discrete/integrated graphics adapter.  When I purchased it in early 2014 the two things it was lacking were an SSD and an active stylus.  I quickly remedied the lack of stylus.  It did come with a 1 TB hybrid fusion drive which I reasoned I would evaluate while SSDs continue to evolve.  I used this configuration for the better part of a year.  I noticed that most often observed slowness came back to I/O bound processes