I have begun to investigate the possibility of doing an e-assist conversion on the my F5, I know some may say heresy to do that to a high racer.  I pulled it off the trainer and started riding it again on the road and realized how much I enjoyed riding it and want investigate a away to extend it use.  We bought my wife an Electra Go last year and I have been surprised at the difference in riding it versus non assist.  For what I have determined my interest are:
    BB mounted drive
    Pedal assist only, not electric drive
    Power for hills
    Still be able to push some speed 25 - 30 when I want
So my questions are
1.  Which system and how many watts?  I have looked into Bafang 8Fun, BBSHD and BBS02;  the Tongshen TSDZ2 750 and it looks like Bosch has selling the mid-bike conversion units.
2.  What rear cassette do I need?  I currently have a SRAM 11-34 9sp cassette and it looks like the drive only come with a single ring in the front in the mid 40T
3.  Will the torque of the motors create problems with the longer chain line?  
4.  Since the F5 has a power side idler will the idler/shaft be at risk?
5.  I have standard caliper brakes and it seems I may have to change those out?
6.  Will the wiring harness be long enough?  I plan to mount the battery under the seat so stretching back up to the BB and the handle bars will take a good bit o cable.  I guess a compromise would be to move it forward and more under the center tube.
7.  Am I missing something to consider here to better understand the impact of what I thinking.
 
I will be reaching out to ECO Cylce or other e-bike supplier but not sure if they will have dealt with high racer conversion and I know this group would know something about that.
 
Thanks for any input.

1. Like Meta Ken, I selected a Tongsheng TSDZ2 500 watt drive to install on my Catrike Speed. I like it because I can set the assist level low and get a workout or set it high and easily ride very fast and rapidly climb hills. I also like the Tongsheng drive, because it's stealthy (the motor housing is small). The Bosch and Bafang drives are larger. I'm using a 17.5 amp-hour Hailong Shark battery and can ride over a 150 miles between charges, if I ride mostly in assist level 1of 4. I have put over 2,500 miles on the drive and have experienced no problems, except a mechanical failure of the throttle, which I rarely use. A good feature of the Tongsheng drive is that it doesn't drag, if the assist is turned off. If you are going to ride where there are a lot of long, steep hills, it might be desirable to order a 750 watt drive with the optional bronze drive gear.  
 
2. Like Meta Ken wrote, you can keep your current cassette. The Tongsheng drive comes with a 42T front ring and a chain guard. You can remove the chain guard and install a 110 BCD second, larger tooth-count ring. If your bike has a 650c x 25 mm rear tire, a 52T "narrow wide" chainring would get you to 30 mph in a 52T/11T gear combination at a little under a 90 cadence on the flats at assist level 4. The non-programmable Tongsheng displays cut off assist at a 90 cadence. The optional programmable displays raise the cadence limit. Regarding the "narrow wide" chain ring, it has longer teeth to prevent the chain from jumping off the ring. ECO Cycles sells it as an accessory. The front derailleur will not work with the Tongsheng drive, so the chain has to be moved manually between the two rings. I've never had to use the 42T "get me home" ring on my trike, because I've never lost assist.  
 
3. I'm using a standard KMC chain on my trike. It may wear out more quickly, but I'm going to stick with it.
 
4. I have a 14 year old power side idler on my trike. No problems with it, after over 2,500 miles of riding with assist.
 
5. The drive plus battery will add 20+ pounds to your bike. Your existing caliper brakes should be adequate. The Tongsheng drive kit comes with brake levers with built-in switches that cut power to the motor when the brakes are applied. They are really not needed (I didn't install them on my trike), because motor power is cut when the rider stops pedaling. Another advantage of the Tongsheng drive is a shifting sensor is also not needed. Bafang drives require a shifting sensor to cut power when shifts are made.  
 
6. Like Meta Ken, I obtained the cable extensions I needed (except for the battery cables) from ECO Cycles. I made my own battery cable extensions from heavy gauge, insulated, copper, stranded cable. I soldered the connectors onto the conductor ends.  
 
7. As Ken has stated, parts have been in short supply. Most of T-Cycle's E-cycle parts have been unavailable, until lately. Noticed the frame-mounted battery support you will need is back in stock.  
See: https://t-cycle.com/collections/all-battery-mount-parts/products/fully-configure
able-battery-mount.  
 
If you decide to go with a Tongsheng drive, you will need to order anti-rotation boom clamp (https://www.eco-ebike.com/collections/tsdz2-accessories-parts/products/trike-boo m-clamp-anchor-for-tsdz2). Like Ken, I recommend ordering a kit from ECO Cycles. I ordered a kit and battery through Amazon. When I received them, there was no info in the packages as to what company to contact for warranty service. The advantage of ordering from ECO is they provide warranties.