Get a BEC for off the shelf voltage conversion, they're pennies

You could use a brushed motor ESC and effectively replace the whole control circuit for the drill.  The power connector connects to your battery, the signal (white) ONLY to arduino and the output to the drills power drive.  Gets rid of the whole power activation circuit.

http://www.hobbyking.com/hobbyking/store/uh_power_Search.asp?strSearch=Brushed+esc

It works with standard remote control output signals, easily replicated with arduino.
Just a thought.

A very cost effective method for powering a pi is using a UBEC

http://www.hobbyking.com/hobbyking/store/__14310__HobbyKing_UBEC_3A_2_6s_LiPO.html#relprodspan_focus

You can select 5 or 6 volt output up to 3amp draw, so perfect for a pi.
It'll draw power from 2S (7.4 volts) up to 6S (22.2 volts) DC source, so perfect for most hobby style LiPo batteries.  You will need to solder some terminals and possibly reconfigure the it put, the white wire is. Signal wire, btw, so you won't need that.  You can either just chop it out or ignore it.

http://www.servocity.com/

Those guys are pretty switched on, and will ave anything you might need.

You're right, there's more reflected wave forms on the deck.  More of a reason to use circular polarised antennae ;-)

So far as staying in shape is concerned, there's only really one chance for it to get bashed in a flight unless you're doing it wrong, lol.

Personally I'd go for a virivent, they "apparently" perform better than a Clover and have a flatter profile.

Two particularly good articles on here for antenna creation

It's often a bit more than just range you need to consider.  A cloverleaf with a high gain patch will also cut out cross polarity interference, something you especially need to consider with a moving object.

Sounds like you might want to investigate skew planar / virivent antenna for your transmission issues.

Big trak?

Why OLED? Is this indoors?  Outdoors?  Under what lighting conditions?

Variable light conditions from full sun to night time, plus OLED more for viewing angle.
I'd considered 7 segment display, the reality is though that it's fixed, dependant on how many segments it has.  The other reality is colour scheme.  It doesn't really lend itself to high contrast black on white for day time use, then night friendly colours - which obviously can be achieved with an LCD / OLED, although LCD has the back light on continuously.

And Liudr, yep, that is also the plan, which ever screen I use, I'll be doing that anyways... for whatever key point of information is in the spotlight at that time (I'm thinking ahead - forgive me)

3.2" might work... any others?

5" would be better

So I'm working on a project that needs a screen to be clearly visible from at least 4 meters (12 ft) away.

The output will be 2 digit numerical with supplementary information being available underneath, the supplementary stuff is not vital to be seen from a distance.

So what's the largest OLED screen available wihtout the price being overly silly?

I'll be using it with a Mega, if that helps for pin assignment

And yes, I've googled til I'm pink behind the ears, but just not getting any joy.

I'll PM you

Hey Jassper... long time no post, how did you get on with this?

Is the board a winner?  Looking for something with more pins and space than a standard Arduino.  Cheers.

Will you be doing a deal with the ITDB02 Arduino Shield v1.2  for it too?

Or at least any updates when it is going to be in stock?  I don't particularly want to buy the LCD if I can't use it

CubeSat FTW