The upconverter allows you to set four local oscillator frequencies by means of internal jumpers; 1100, 1115, 1130 & 1145MHz. Purely for ease of arithmetic and round numbers, I set 1100MHz. Big mistake! Although it still works, it puts the output someway down the output bandpass filters curve. By setting the local oscillator to 1130MHz, I am getting 10-12dB more conversion gain at around 50dB, the claimed figure and the output is close to the curve peak. I suppose if you wanted, you could tweak the helical filter cores, but since both are brand new, I don't want to do too much yet! Both examples here were consistent in their results.
The moral of the story for anyone who has one of these devices is to use 1115 or preferably 1130 as the local oscillator frequency!
PS: Roberto has now advised that the two helical filters on the output can be tuned in the range 1240-1300MHz. It would seem the factory default is in the middle, 1270MHz, so choose the LO to output as close to this as possible for maximum gain.