Bunkie,
You may find some of the fonts that I have created and distributed over the years to be of use. I used to offer these for free download on a web site, but it died earlier this year, so I am attaching the pack of them. They are pretty widely used by skinners, modelers, decal guys, etc.
I haven't seen a good photo of the lettering on the Short planes you referenced, but a few of these may be useful at least as a starting point in terms of general proportions.
The font called "Camp Borden" is the most recent one I did, in 2018, and it was intended for 1920s Canadian military call letters, but it is similar to the general civilian style in use in the UK and Europe in the 1920s and 1930s.
Other possibilities are RAFWW246 and RAFWW258. These are both generally intended to represent RAF 1930s-40s serial and code letters, but differing in proportions, with RAFWW246 having a 1:4:6 ratio of stroke/width/height and RAFWW258 having a 1:5:8 ratio.
None of them is likely to be perfect for your needs, but if you play around with bold type, and mess with the ends to get that diagonal clipping that you see on some fonts of the period, they may be adequate. I think I can at least promise that they will be a better starting point that Calibri or Arial or whatever.
August