After doing a good amount of searching I couldn't fit a good VTail build guide. So I just followed the rough rule of thumb to keep the distances from the props equal.
I just laid it out on card. The first rough draw up was 350mm between the front props.
The next day after some more thinking about it I reduced the size to 250mm between props on the front and I went for a straight bar to mount the front props and the V from there. Based on a 45degree rear prop angle the distance between the rear mounts is 120mm. The below picture shows the rough frame design and proportions. This is using 8x4.5 SF props.
I quickly bent a 10mm U tube to 45 degrees get an idea of the rear prop angle and to make sure that I got the clearance right.
The next part of the design will be figuring out what to use for the plates to mount the booms to and how.
My 2 current quads, a RCtimer 450 frame and a home build 300 frame. I fly the 300 more as I get 10min flight time on a 2200, 3S.
Looking forward adding the VTail to the mix.