No worries, honestly I love working through these little problems, and its been interesting to test out different things!
I cant be sure on wether the behaviour is frame rate independent, but considering 'simulate control' effectively runs every tick, you would imagine it might be affected by frame rate changes. Try experimenting between that and the bullet behaviour for best results is my best guess. As is so often the case, wherever possible playtesting should give you the answer!
Glad to be of help!
You've been a huge help - this topic has been very interesting! One last question though:
Would I be right in thinking: System| Every tick - Player Object| Set Platform vector X to Self.X+250*dt
Is regulating the X movement of the player object by dt therefore making it frame rate independent?
This doesn't really seem ideal though...
As far as I could tell after some quick prototyping the platform and bullet behaviours aren't actually frame rate independent (unless someone knows otherwise). This is obviously a problem for me so I need a way of making the movement robust to changes in frame rate!
Even after a few years programming I'm still yet to realise it's never, ever simple!