Getskay

The only VM II firmware that I know of is the one on this very forum (it took a bit of searching to find it):
 
The file name is VMII 5K_3K MAIN_V2043.rar, but it fact it contains 20.44 (as reported by the QVFW command). There is mention of Inverex, which sometimes have unusual power ratings (e.g. 5200 VA instead of 5000 VA), but this one seems normal. There's a slight risk that it won't work, then you'd be stuck, and would have a genuine reason to plead from your supplier for the latest update 🥺. The above says 180 downloads and three thanks/likes, so presumably some people have tried it. It appears to be about 7 months later (June versus March 2018) than your machine.
The same firmware also runs 3 kVA models; the firmware tests the voltage at some pins at startup to decide which model it's running on.
 

Look at bottom balancing for your cells . Some guys running home converted Electric vehicles do this and they don't use a BMS. I'd still prefer a BMS

I've heard of this way of doing things before. I would however check them carefully every now and then if it was me. Maybe I'm just overly nervous... :-)

OK Getskay. Where/ or from whom did you get the CMax batteries from. You may be able to get a BMS from the same source. If not the is lots of information on the internet.
https://www.youtube.com/watch?v=MZyY1dpka7c&t=4s
https://www.youtube.com/watch?v=SomW_Bx-ECc
Here are a couple of links
 

Well... I'd be more concerned about the high end. At 57V an imbalance is of more concern than at 44V (which is quite far away from the low that Chris mentioned). But better to be safe than sorry in the long term.
There are commercial BMSes on the market, for example BM123, REC, and Orion. None of them are particularly cheap. There are others on this forum who has done their own setups, the so-called "DIY Powerwall". Better ask them... :-)

Then I suspect the term "engineer" is used very loosely 

Without a BMS you can destroy a cell by discharging too low, or cause a fire by charging too high. The cells are not identical and though they add up to 48V (for example), it doesn't mean that each cell is at 48/14 = 3.4V. Some might be at 3.6V while others are only at 3.2V. When you discharge it to 44V,, Some cells might be above 3.5V, others might be below 3V at the same time. Lithium batteries are destroyed if you discharge them too low.
The BMS watches individual cells and disconnects the battery if one goes too low or too high. Additionally it can also balance the cells. This becomes more important as the battery gets older.

https://en.wikipedia.org/wiki/Battery_management_system
 

Many thanks Chris; for battery cut-off, I left it default 44, are you advice to change Back to grid voltage to be 44 also?
for your question, I don't know what is BMS, but I can attach image for what exactly I have, additionally I installed 48 volt vent FAN on the right side up :