This goes against a lot of what is written here, but it is another perspective. I know some people will dismiss this (and in many ways I dont blame them) but I do instruct close formation by day, and I know this is not what you do in reality, but playing BMS is quite different to reality :eek:
A key thing I think worth mentioning is that flying formation is BMS is much harder than doing so in real life. This is due to a number of factors, but primarily due to the poor cues for rate of closure, and also lag. In real life the graphics are better, you can see every rivet of the lead aircraft and therefore very small changes in closure can be picked up instantly. Not only that, there is no lag, so you will see them instantly and your aircraft with react to your inputs near instantaneously. Milliseconds of lag that were never a factor in game now are and can easily induce oscillations. For this reason I use a technique different to what I would do in a real aircraft- I actually scan the HUD very quickly. 90% of the time I am looking at the tanker, but every couple of seconds my eyes come onto the HUD for 1/4 of a second. This is because until you are latched and get the lights, typically your most precise and accurate (not necessarily most obvious) cue for rate of closure comes from your airspeed which does not suffer most of the errors a typical IAS system would. If you establish the base speed of the tanker before you start you can very quickly judge small amounts of closure from your own IAS.
Also if you are suffering PIOs (pilot induced oscillations) in pitch, make sure you are perfectly in trim at your tanking speed before you start. You can do this when you stabilise off the tanker wing tip.
As also discussed previously, throttle movements should be microscopically small. If you are starting to throttle bash or pitch up and down, relax on the controls, take a breath, wiggle your fingers and stabilise.
Just another perspective, sorry the sound is low.
Just remember I am not looking at the IAS, just scanning it very quickly while looking at the tanker/lights.