Sketchup is an easy program to use and its very clever..much neater than pencil and paper and quicker once you've played with the program for a while, you can do 2D lines very quickly , and go on to make a full 3D model if thats what you want..
All my drawings are done in sketchup...and in my previous post the sketchup file for my version of your radius is in the zip file..it took about 10-15 mins to draw up.
Try downloading sketchup and my zip file, then load up my drawing and correct it to suit your build..
having a problem to work on, like the changes will get you learning faster..
the basic version is free.. the pro is time restricted...
You will realize I am just as much a sketchup fanatic as I am a KF fanatic... however, on using sketchup, although I can very quickly do basic line drawings, I have a long, long, way to go to make use of its full potential
Power for the radius... my setup is a 7x3.5 on a 800mAh 3 cell and a 1700kv motor.. this is drawing about 7-8A at full power and hovers at 1/2+ power...so my max speed is going to be less than Thomas, but it will go vertical just fine..
My AUW with an 800 3 cell is 9.5 oz.... total area 1.8sqft... so 5.3ozsqft..
When going to 2 cells use a fairly high kv motor and prop it to suit, but dont expect the same max speed as thomas unless you take the motor's kv well high..
Your choice of power setup obviously depends on what you want it to perform like, My site is a sport field at the bottom of a park,so I tend to restict my models in top speed so as not to scare the pedestrian trafic..
The funbat is another good simple to build model, it reminds me of the much earlier obilex sloper and its layout is similar again to the radius, like a lot of our models it uses similar ideas, with changes of shape to produce a nice new model.. It then just depends on whether you like straight lines or curves...