Thanks for the advice.
In Ver1.0.3, I was able to get 240mph with 0 boost.
However, after Ver1.1.0, I can only get 200mph with 0 boost.
As for the rate of climb, I need boost +6 to climb at Vy (180mph), and the rate of climb at this time has been reduced to about 2000ft/min.
I have never flown a real Spitfire, so I do not know if the performance of Ver 1.1.0 is realistic or not.
However, I am puzzled because the power has been greatly reduced compared to Ver1.0.3.
From the 1.1.0 release notes:
It’s not really surprising if the performance is different after those changes. Hopefully it’s more accurate than before, but never having flown a spit IRL I wouldn’t know.
I did a couple of takeoffs from external view, side on, to take a look at prop clearance. That was certainly an interesting experience!
Stick neutral on the roll there is still enough clearance, albeit not by a large margin. With +1 trim rather than -1 there is unsurprisingly a little more. With a bit of back pressure to keep the tail lower I found it took off before it was ready and wasn’t so under control. I’ll play with this a bit more when I get more time.
Now I know why I’m not getting the speed I want.
By removing the external fuel tank, I was able to achieve a speed of about 240mph (at 3500ft) at zero boost.
That’s exactly the problem with +1 trim. I did some testing yesterday and found that I had to get the airplane level just as it lifted off so it could build up speed.
Whatever the trim, the Spit seems to want the pilot to be really nimble on the stick all the way through the takeoff sequence.
Was just thinking - it seems like an obvious thing but, since we’re switching back and forth between +1 and -1, maybe neutral is worth a shot.
Will try that next.
Makes complete sense.
The Spitfire is such a finely tuned airframe that anything you hang on it is really going to affect performance.
I still find the Mk IX a bit unruly compared to the (A2A simulated) Mk I. That felt balanced. The Mk IX is more responsive in the air but it’s not as refined - and that really comes through on takeoff and landing. The big engine throws it off.
Glad you’re (literally) up to speed… 
Yes for sure you have to actively fly this, especially on the ground, process makes it easier and possible but there’s no letting the bird fly itself, until it is stabilised and trimmed in the air.
Great to see how you compensate drag from the gear and flaps on approach with just tiny throttle adjustments.
Apart from taking off ( which can be a b*tch on it’s own to master) , landing this bird is also ‘interresting’ and requires a lot of training 
Ten hours according the Air ministry old boy and after that it’s on the job training. OJT to be carried out at Sqn level. Facilitation, of course, is entirely down to Jerry 
I highly recommend Geoffrey Wellums excellent “First Light” for all you budding Spitfire pilots. Also Tom Neils “The Silver Spitfire” both available in paper, Kindle and Audio. Both give some nice tips on flying warbirds…
Thanks to all the advice on here, I bought the MkXI just before Christmas and have thoroughly enjoyed myself in her.
I keep my engine down to 1800 on brakes, then as she starts to roll I up it to 2000 with stick back halfway. After the veering to right and left, I bring her up to 2650 and allow the tail to raise, with a touch of right aileron. As she starts to bounce I pull back again to leave the ground and increase the engine to 3000 for the climb. At 500 feet, close canopy and settle in for my half hour flight of playing with the trim to try to get it right 
I have two MkXI questions.
The canopy, door, & lock are controlled via LVARs (local variables) so no there’s not a straightforward keybind, you’d need an external control program like Axis & Ohs or SPAD.Next.
I think the battery is an in-sim command (toggle master battery) so it should be possible, I’ll have to check when home (if someone else doesn’t answer before)
You are absolutely correct, now I can start the electrics without having to angle around the throttle to get to the switch. Nice one Dude.
Sounds like you’ve got it solved, but for the record, you can also trip the battery switch by shoving the throttle forward, which is how it was done in the real aircraft.
To turn it off, though, you’ve still got to reach under the throttle - so your switch will come in handy there in any case.