Hi there! I think you spoke to me and my dad? (mines the blue X11, my dad runs a Nemo coloured X10)... first things first, congratulations on your purchase!!!
the stand up servo as said is a modification using a low profile servo, hopefully ill be getting mine this week! you should come to southport this weekend instead LOL ...
I run a Nosram 6.5 in mine, with a 72 spur and a 19 pinion its just right, enough top end and plenty of low end torque.
spares you may need:
1x spur gear, wishbones front and rear, and some front and rear hubs.
i would also advise some of the new rocker pivots which are coming out, as the X11 ones are weak and snap easily, and also the M4 titanium turnbuckles. cant think of much else...
ill be down at southport most weeks and ill be doing the last regional at Bury so if you need any spares or help, just give me a shout
Regards, Tom