Converting a Recumbent for a friend - Questions?

[Bikengineer]

I've been asked by a friend to convert a bicycle to electric for another friend.
My mate works in China and can send over conversion kits cheaply. His mate rides a recumbent trike due to a motorbike accident years ago. His recumbent is a nice bit of kit and he racks up some serious miles not being able to drive a car. The recumbent is a HP velotechnik with 2 front 20" wheels and a 26" rohloff hub wheel in back. It's actually built for 20" wheels all round but has lengthened dropouts to run the 26" wheel.
I went to assemble it all only to find the 26" e-kit he ordered is a front wheel. Can't use that and it will be resold but thinking conversion would be best with a 20" wheel in rear and abandon the lengthened dropouts? That will give more torque fit the original v brake mounts.

Questions
-what gearing will work? He is a strong pedaller so I'm thinking a road cassette rather than mtb. Do rear hub motors come with a cluster or cassette system and how many is possible? I'd like it to be indexed and of high quality. I have a short SRAM derailleur and want max number of cogs as there is no front derailleur. Also want to maintain some clearance between road and derailleur.

-bottle batteries are easy to get but not sure where to mount was thinking behind seat in a pannier as the rear end uses a swing arm with suspension which means minimal locations to mount it. Open to different ideas? The rear pannier rack is a bit bodgy as it was modified to fit the 26" wheel.

-brakes are currently 2 discs up front operated by one lever and v brake at back. Will the e-brakes in kit be designed for this or older caliper / cantilever style? Am thinking of leaving discs as they are and fitting e brake lever only to rear brake.

 

[Bikengineer]

Other ideas kicked around were crank drive system but there isn't much metal to mount on as BB is at the very front. Getting 2 drive wheels in 20" would be cool and he could retain Rohloff but I've never seen such a kit and imagine there would be differential or controller issues?
Was thinking a 350w kit would be close to legal and allow him to mingle with cars as most speed limits here are 50kmh. Also thinking 350w may not require a rear torque arm?

 

[docnjoj]

At the very least you will need at least 1 torque arm. HP's are alloy frame.
otherDoc

 

[torker]

I have recumbents but all mine are 2 wheelers. I would not worry so much about gears. Mine never comes out of hi gear now. You should search for trike builds here. Most batteries are mounted below the seat along the frame both sides. You will have to fab something. A 20 inch wheel will have better torque but it will make the derailleur lower. I never liked this on my recumbent dual 20s . There are some great trike builds on here Doc Bass, Recumpence and others. Welcome to the sphere !! Ebrakes will work good for the rear.

 

[docnjoj]

+1 for above, torker. I have batts under my seat in a Lexan rack and the balance is fine. I use 20" wheels cause I like the torque. My top speed when I used 54 volts was about 30 or a bit over (mph). Now I use 36 volts and get 20 or a little over on level ground. Both my wife's trike and mine are steel but for her front drive 9C I use 2 torque arms for safety. My rear motor has 1 T.A.
otherDoc