My opinion on a few things 
Eggbeater vs Drum:
A featherweight Eggbeater is way more expensive and complicated than most people think.
You can't put the bearings in the weapon so you need to build bearing blocks.
These need to be aligned else the weapon generates too much fiction.
If you have a mill no problem.
Then you need to build the Eggbeater. The best material for this kind of weapon is Hardox.
The Hardox must be thicker then the shafts you want to use, mine is 25 mm with 20 mm shafts.
You need to get the material cut by waterjet with a minimal taper.
The waterjet company has to cut the material slower and this will make it more expensive.
If you have a big taper the weapon will not balance well and shake your robot to bits 
Then you have to turn the shafts from square to round shafts.
You need a big late to make the interrupted cut on Hardox and a even bigger late to cut the radius from the shaft to the Eggbeater.
Aligning is a pain and it you can't do the job yourself you have to pay a lot for this part.
The pulley needs to be connected to the Eggbeater and should not weaken the shaft, this is already the weakest spot in the Eggbeater.
All these things make it expensive and harder to build... so be aware.
Easiest way to build a weapon (in my opinion)
Use a dead shaft and build a drum with disks on both sides.
The dead shaft makes the alignment easier and you dont need a mill to make the holes to mount the dead shaft.
On a small lathe you can make the bearing pockets in the aluminum drum. If you dont own a lathe then many people will do this for you at minimal cost.
The holes to mount the disks can be made on a pilar-dill. Just create a template on a 3D printer.
Get some disks, again Hardox is your friend 
Make the mounting holes in the disk part of the big hole in the center, this is cheaper to cut!
The inner hole should be cut with minimal taper, the outside can be cut faster, again cheaper to cut!
Get some shoulder bolts to mount the disks. Make a groove in the drum and your pulley problem is also solved.
Don't make this type of drum to wide this won't work well.
It all depends on what you can build yourself.
Outsourcing complicated parts/jobs is expensive.
For speed and wheel size:
I like 80 mm wheels and 700rpm (minimum) to 1000rpm on the outgoing shaft for both Raptor and Featherweight.