Tom, here are some tips for when you braze a kickstand plate onto your wife's bike (after you have allowed enough time to mourn and recover from the loss of what you wanted to do). Braze an M10 SS washer over the hole. Put the curved side down next to the plate and leave the flattest side up. That makes it easier to braze and the kickstand washers prefer resting against the flattest side. This has to be done with silver (56% works fine). Do this before brazing the plate to the frame. While it isn't as important, I also braze the water bottle boss in the tab to hold the fender before brazing the plate onto the frame too. After it is painted the paint can be removed from the top of the washer. Now the kickstand's lock washer won't scar the paint. The washer provides additional strength to the plate. That long kickstand arm has a lot of leverage that the kickstand plate has to withstand. Which reminds me that you must braze on the plate with brass and not silver. I made the mistake of brazing the 1st of our Messenger bikes kickstand plate with silver and it couldn't withstand the forces of kickstand.
The position of the plate on the frame will depend on where the tab w/bottle boss places the fender. Ordinarily this is the same distance from the rear axle as the seat stay bridge. It is always a bit of a trick to get it on straight (so the kickstand will be positioned properly against the frame). I use an adjustable parallel but there are other ways. After I get it in position, I put a very small spot on one corner. Then I check to see that it is square and if not it can be adjusted (I usually gently hit is with my little brass hammer). When positioned properly spot the other side. When you are ready to braze it up, 1st braze the side you originally spotted. They take a lot of heat.
You might need to trim the edges to match the angles of the chain stays. Do this before brazing the plate to the frame. There is no reason for them to be sticking out much beyond the stays. When we get together for another fillet brazing session, we can do the kickstand bridge if you are that far along on your wife's bike. If not we can do it on one of our Ukraine frames. I can do it and you can blame me. No wait you want credit for adjusting to your wife's request so never mind.
Here are some pictures of brazed on plates before and after. One time I couldn't find a supplier for these plates so I made one out of flat stock. Fortunately I had the drawing from the company that makes my laser cut fixtures in Ukraine. You can see the pattern before bending in the middle plate.
This is on one of our transportation bicycles we make for pastors in Ukraine
This is on my personal bike I use on bike trails
These are the kickstand plates I have made in Ukraine. Those are M10 SS washers I braze over the center hole.