It sounds like a great project. I've put a lot of thought into such a vehicle, a highway speed capable electric with long range and protection from the elements. I want something that is practical enough for everyday use and has absolute reliability. I do believe some of your criteria and priorities need some tuning. Here are my thoughts:
A place to gain an understanding of your power needs is the HPV calculator at
http://www.kreuzotter.de/english/espeed.htm . Delete the amount in the power box and input a speed. The info for the Quest velomobile is probably your best match, and then enter your own weights, elevation, grade, speed, etc. It's a great tool/toy I use it all the time.
Weight- Unless you're already experienced with carbon fiber, I don't think sub 60kg is reasonable, but the good news is that other than during acceleration weight has only minor affect. It has minimal effect on energy consumption at cruise. Of course you want to strive to minimize weight in the plan, but for a solid enough vehicle with the needed 2-3kwh battery and a durable drive system capable of your needs I think with good weight management you're still looking at 80-100kg.
Greatest efficiency and greatest practical efficiency are two quite different things. The former is an uncomfortably small vehicle (to make the smallest hole thru the air) with a thin shell that's light and noisy inside, which is used to for record attempts or in competitions, not pleasure cruising at high speed. Since you want highway speeds and 160km range, the most important thing is aerodynamics, and the example in your picture seems like a great starting point, though for practicality include some nice cargo area. The other primary part of the equation is drive train efficiency. While hubmotors have some specific compromises, nothing can beat the durability and efficiency of a real high efficiency hubmotor (no not those commonly used on ebikes on ES). For durability and greatest real world efficiency you have to build for maximum load conditions. I'd need to know your weight + potential cargo, maximum grade for hills of 1km or more, along with road conditions, to calculate power and torque needs to make recommendations.
Speed- If you want to be able to maintain 110kph up a 5% grade your bike needs to be capable of 130kph or so on the flats.
Other- You have a motorcycle, so I'd strongly suggest planning for comfort and good performance or you won't want to ride it much. eg You don't shop for moto tires based on rolling resistance, so worry much about it for your electric velo. So what if it adds a bit to your battery pack. You'll want much more battery anyway, not so much for extending static speed cruising range, but more for chewing through more energy with exhilarating performance on shorter range trips. You'll have a fun road rocket and 1kwh will just be a tease and leave you with all kinds of range anxiety.
Construction- Sure tubing is strong and rigid, but it wastes space, which is a huge premium on such a vehicle. That probably means punching a bigger hole through the wind. You'll need air flow, both over your battery pack and over your motor.
Batteries- The latest 18650's are great, but if cost is a priority, I'd suggest looking to batteries salvaged from electric cars. I'm extra frugal, so $250/kwh or less is much more appealing than $1000/kwh even if it adds a few kg to the pack. I'd feel safer enclosed in a tube with an already proven through time and usage battery that was over-engineered, than one I DIY'd from new cells. An e-velo isn't like an ebike or emoto, where slowing quickly and jumping off even before a full stop is possible, so only a cell chemistry incapable thermal runaway would be acceptable for me. Of course I can say that easily, since I already have plenty of A123's, Nissan Leaf modules, and Chevy Volt modules to make several of the packs required. 8)
To me the biggest issues are steering geometry and the suspension. Due to the long low vehicle shape, the geometry isn't something we can easily copy from a known example like is possible with a bike or moto. With the recumbent position and high speed, the pilot will be especially sensitive vibrations and bumps, so you'll want a rear shock that is very adjustable.
I look forward to seeing your project progress, so please share regularly. I know there are a number of us wanting to build similar vehicles, and collaboration could prove beneficial to all. In my case, I need to fit enough extra batteries for a 280km run without recharging, and in the middle of that run there's a 1600m altitude climb that has some long 10% grade stretches. Thank goodness I don't need the high speed you want, at least not for the long run.
John
