Thanks for the replies. Forming up this four ship was fun to do although the crew nagging me for feeling sick because of all the minute adjusts I had to make has not gone down well in the mess!. I'm building up to a 12 ship combat box.
Because of the modelling of the boost control in the B17 it's relatively easy to maintain close formation with just slight adjustments to airspeed +/- 1 or 2 knots.
I'm hoping to add an escort of P47's, P51's and some FW190's.
I've no idea how many airplanes FSX can handle but it shows no difficulties with four.
What's interesting is when I order `bomb doors open` ALL the planes go bomb doors open.
Wonder what will happen to the escorts?