After hearing many positive reviews about the patterns from Truly Victorian and specifically about the TVE01 1903 Edwardian corset above I went ahead and bought it. I am now among those who praise the patterns drafted by Heather.
So far I have managed to put together a mock up. The size used is one corresponding to a 3'' waist reduction and after trying it on I believe it to be spot on. The mock up is made with the fabric MINNA from Ikea. It is a sturdy fabric available in several colours that is easy to work with. I do believe that it would work very well for a finished corset without stretching but i do not dare to risk anything and have already ordered a herringbone coutile.
For my first fitting I did not add any boning and it was a total disaster. After that I was prepared to pick a larger size and make a second mock up. Luckily I decided to sew some boning channels on it and inserted zip-ties left over from a bustle I recently made. That made all the difference in the world and proved that I had indeed picked the right size. There is a considerable gap in the bustline but from what I have gathered this is historically accurate and the patterns includes bust pads that will help fill it out
This picture is from the second fitting. I have not added quite enough bones so there are some wrinkles which I think will smoothed with the additional padding. The reduction looks quite extreme but it is really very comfortable, much more so than my previous victorian corset. The pressure is all in the waistline and nothing on the ribcage whatsoever.
At the moment I am patiently awaiting packages of supplies from VenaCava and SewCurvy. In the meantime I will alter the pattern so that it is not quite so high and maybe let out the hips some. I have high hopes for this corset.