Hi Jason
your pipe looks OK don't give it any more down thrust as it will make it very unstable in the air with power on and you would run out of elevator, dont worry about the heat it is not an isue as for elevator travel you can dremel out a bit to give it abit more travel
around 50 mm each way is fine
what turbine are you using make sure you have 30lb plus hope this of some help to you

regards
Andreas