Here is the definitive freewheel spider company, 4 arm, 5 arm, and you can mix and match them ...
http://bikemotive.myshopify.com/products/freewheeling-crankset-for-ebike-bikemotive
I went cruising the web for spiders the other day and discovered that trials bikers use freewheel cranks previously I only knew about them because it came in my electric bike kit.
And here is the definitive high quality bolt to freewheel for cranks made by White Industries which also makes your single speed chain ring freewheels that are used heavily by trials bikers ...
http://www.sickbikeparts.com/catalog/product_info.php?products_id=62
White Industries freewheel chain rings, notice scroll down the page "Trials freewheel" 72 points of Engagement ...
http://www.whiteind.com/free-wheels.html
I notice there are quite a few freewheel cranks available in the UK but only a handful of North American companies carry them, because trials is popular in the UK but not the USA.
I built a very powerful electric mountain bike, 85 lb, I weigh 200 lb, up to 33 mph and climbs like a billy goat. I have ridden it frequently for the past 2.5 years where I used the cheaper version of the freewheel and it worked great, I never did ANYTHING to it, never oiled it, it just worked! BUT there was a LOT of lag in the freewheel!
These are available all over the web, I think Amazon has them a couple bucks cheaper ...
http://www.sickbikeparts.com/catalog/product_info.php?products_id=178
So now I am building a second eBike with higher quality parts to see what its like and you benefit from my research.