Hi all- just a quick question about departing IFR from uncontrolled airports. As a low time IFR pilot, the few times I've departed IFR from an uncontrolled airport I picked up my clearance on the ground via my cell phone from the local TRACON, usually while sitting in the airplane just before starting the engine. After copying and verifying the clearance the controller always asked how I'd like my release. I always said that I'll call back on the same phone number while holding short just before take-off. During this second call I got a release into the system and my void-if-not-off times, then departed via the ODP within my window, knowing all the while that I'm in the system and free to enter the clouds. Once high enough, I contacted departure and away I went... That's all well and good, but what if there's unlimited visibility and say 4000' AGL ceilings, with no troublesome obstructions nearby? Rather than tie up the uncontrolled airport with my IFR departure, couldn't I get my clearance from TRACON on the ground, depart VFR, and activate my IFR flight plan when comfortably aloft. How does this work? What would I say to ATC on initial contact? Would they know that I already have my clearance and I'm just looking to get into the system? Would I squawk 1200 on departure (since I'm departing VFR) and switch to my assigned code after making initial contact? And how would I know that I am officially IFR and legal to enter the clouds? And finally, what if I was further away from busy airspace, taking off from a sleepy uncontrolled airport in unlimited visibility and 4000' AGL ceilings, and opted to get my full clearance while airborne after departing VFR (maybe because cell reception was poor on the ground and there was no good way to get the clearance over the radio while on the surface)? When am I officially in the system and legal to enter the clouds? Is it as soon as ATC confirms my read back? Is it as soon as they tell me to squawk the IFR code?