@ yankees.

I purchased this item  in theory it will put out 220v +/-  5%  so 209-231

https://www.amazon.com/gp/product/B071V5NXZV/

My input is 243.1 and my output is 220.7 on my hand held meter

the meter on the unit read 243 in and 220 out.

I am testing it with an old s7ln  before I put it on the s15

I will post a photo very soon.

Since it is the 5000va model  I think  it can do 2 units.

of course you need to feed 240 in to run 2 units.

I am using this to stabilize not step up 120 to 220  or step down 220 to 110
To be safe I am running a cheap piece of gear on it. Not the s15