Just start the GHB a bit later than the 4-FA, if the GHB wears off when the 4-FA comedown comes on your gona feel like shit for a good few hours, and be tempted to do more GHB. Personally I'd just take a dose of GHB 2 hours before the end of the 4-FA and one final dose of GHB at the same time you run out of 4-FA so you get a good sleep from the G at the end.
Indeed I was dreaming about waiting till the 4fa magic faded before adding ghb to the mix. Really just wanted to make sure it was safe to mix the two. Many thanks for the info.
you might want to turn off your phone because the G will have you even more lovely dovely then normal and you might text some girls(or otherwise) you like about how awesome and cute they are.
Do'h.