Forget that part about only changing rears, i think it´s very possible to do but the question is how many seconds whe are talking about in terms of getting away quicker out on track vs hauling those seconds in over what 25 laps or so.
I say, full tank from start, change all tyres just to play it safe.
About pitstop, It´s difficult for me to tell you when to pit since everybody has a different feel on when the right time is. but aim at a little more then half length - 29,30 or so. You will feel that yourself.
Just come in as you always do to pits, brake earlier to play it safe, make sure your under the speed limit before the cones, slap on the pit limiter and full throttle right away. Always good to do some practice runs so it´s nothing new to you.
Just glide down the pit and brake in front of your lollipop man, make sure you take it easy since the last thing you want to do is back up etc.
Oh and btw. when you standing on grid, go to the black box and uncheck fuel. then you don´t have to worry about anything other then coming in, change tyres, wait for lollipop man and go.
You can practice them as much as you want in practice. Just do some laps (doesn´t matter) com in to pitlane, brake, pitlimiter, brake in front of him kinda, the tyres are getting changed, and then just drive out when he lets you.
I will probably do a race later tonight but what time where you planning on doing? 19:00 GMT, 21.00 or 23.00?
Maybe we will see each other on track
Don´t forget to update Trading Paints, i have a new skin on my baby