I didn't adjust any of the settings h0ughy, just swapped the barlow around. You are going to get a loss of brightness no matter what method you use to increase scale. All that would be needed is an adjustment of gain/gamma.
I learnt something else the other day to (the hard way of course. Is there any other way
) Normally I have my laptop screen pretty bright when I'm planetary imaging at home alone, but the other night out at Ron's I had it turned right down. This had a direct affect on my ability to judge gamma, gain, brightness, saturation etc in relation to my exposure and frame rate. Consequently when I processed them at home the results were not as I expected. Most ended up with some onion rings from being underexposed.