I've had an evening of it, trying to get the flash to work on the Holga, it's an FN, mind. It's not going to happen. So I've gone mad and paid over the odds for a 120N online. See, I've got a 1970s flash gathering dust in the cupboard, and I want to use the three rolls of Fuji Velvia that have been in various fridges across the world.
This nadangergeo is using a 120N with flash but with Provia xproed. Be interesting to try double x-ing a white person with dark hair and clothes, to see what occurs with Velvia. More redness, probably, but let's see.