I am attaching the application structure I used. It is in Word form, so feel free to download, change and reuse. This was my SET (O), so don't focus on the actual documents attached but rather the structure. I used a similar for my first extension. Both were approved in about 8 weeks - not super fast, but not too bad either.
There is the cover letter which sets out the variations that I thought I needed to point out. I did not add any additional documents for the genuine entrepreneur test since I felt the job creation documents already provided that. So, I just added a few points in my cover letter.
And then, I attached all the mandatory documents organised as one section for each attribute with a cover page for each section summarising what was included.
For any sticklers, note that maintenance fund evidence was not needed for my SET (O). That was my error, but it was in a separate section so easy for the CW to ignore
Also, my Job 2 was in a business that I had joined, so the additional documents for that.