Not an expert here but I'd suggest getting the parts together and building the chassis around them, otherwise you'll find it not fitting.

When starting projects like this I like to write out all the parts I'm going to need, either in a word doc or a spreadsheet or a piece of paper, then exactly what I will get, and then what the price is. For example: from a model plane I put together this summer:

----------------------------------------
Material
http://www.wickes.co.uk/Polystyrene-...x2-4m/p/210801
£6 ish

Motor
http://www.hobbyking.com/hobbyking/s...6247&aff=98656
$13
http://www.ebay.co.uk/sch/i.html?_tr...at=0&_from=R40
£16

Battery
http://www.hobbyking.com/hobbyking/s...9493&aff=98656
$15 with postage
http://www.ebay.co.uk/itm/TURNIGY-13...item259055ac6b
£10

ESC
http://www.hobbyking.com/hobbyking/s...5202&aff=98656
$10 with postage
Or AW one
Servos
http://www.hobbyking.com/hobbyking/s...9549&aff=98656
$2 x 2
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This gives me an idea of the cost of the project before I start, and means I can make sure everything will work together and be within weight etc. Might not work for you but it works for me