Nice read and your experience with the SG-LAB transverter is similar to ours in vk1 where we now have 5 or more of them. Several of us also have their 13cm transverter too.
The stock 2 el antenna works surprisingly well but when you upgrade the antenna to a longer one you start to consider 100 km a routine contact. I have used mine with a 4 el yagi and with an 18el yagi, with good results.
I just realized you have a whole site devoted to 23cm SOTA which I need to ferret around and filch some of your antenna ideas to get beyond the stock 2 element SG Labs.
There is confusion between VK1AD (who has the blog you mention) and me (VK1DA). Similar looking callsign and the same name… he is the AM for VK1 and I am the AM for VK2. We have activated together many times.
For this reason I sign with both my callsigns to give further clues as to which one I am.
The antennas he has made are very well constructed and work fine too.
He would be pleased to know you are reading his 23cm blog.