Inspired by this I thought I would try something similar with my A4000.
I bought one of these which lets me mount the mSATA drive in a zorro slot (£17.90):
https://www.amazon.co.uk/gp/product/B00J3XT7E0
It seems to work well and HDToolBox recognised is straight away.
There is no master/slave jumper, it only works as a master. No biggie.
I'm using a KingSpec mSATAIII 32GB drive (£12.99):
https://www.amazon.co.uk/gp/product/B01HMD6JIE
I'm going to need a molex power extension as power doesn't reach the zorro area well.