I've done the measurement. The battery is 105cm wide (or so - I'm not going under again to measure to the mm).
If the bolt holes on your cage are further apart than that, you can bolt through. Ours aren't, so we popped to Cheltenham to Cleevely, EV specialists, who dropped out the battery and allowed us to use their lift while we fitted the tank. Overall, the job was five and a half hours. At £100 an hour it cost £550.
Now we know what we're doing, I reckon it would be around two and a half to three hours: 45 mins for them to disconnect and drop the battery, 45 to refit and the remainder would be our fitting time. The biggest time vacuum the first go around was the endless measuring to be sure that the tank would fit and that the bolts and spreader plates wouldn't interfere with the cooling fluid pipes on top of the battery. Here's a pic of a battery to show what I mean:

Handful of points:
I don't care how anyone else fits their tank. All I care about is how we fit ours. There are 382,766 other threads on that subject, all exactly the same.
Braking - the only comment on that is that it stops quickly enough for me. Everything I've read on EVs says to do a proper emergency stop once a month or the brakes can seize from lack of use. When I've done that, it stopped plenty fast enough.
The only experience I have is of Stellantis EVs (they all come from the same factory so they are all the same) and a Gardiner tank (the forerunner to the Grippa offering). We chose a Stellantis EV because it was insanely, bizarrely, stupidly cheap, but they are now even cheaper - there was a 36k mile, grade A battery 2021 Citroen e-Dispatch up the other day for a buy it now of £8,500 + VAT. Potty. If Transits were even close to that we might be looking at them. A van is a tool for us; the cheaper the better.
Vin