No Runningbackstays on E33
Well, as an E33 (hull #25) owner for 24 years, I'll take a stab at your question about running backstays. Our boat came from the factory without any. The original owner sailed out of San Diego and raced the boat regularly off shore and, as I recall, did a Mexican race, or two. I sail on the Columbia river here in Portland Oregon, and for most of those 24 years I actively raced the boat. Sailing on our river can be quite "interesting" on occasion with a strong downriver current and strong upriver wind - big short chop! As mentioned - no backstays - no problem on the 35 year old boat. With a competent racing crew, we would routinely charge in the steep chop with full main and a 130 jib in 18 to 20 knots of wind. Lots of weather helm requires a good man on the main sheet and a fully tensioned backstay (upgraded to a hydraulic system). Never felt the need for running backstays - YMMV.
FWIW: I have found that a 130% head sail to be near ideal - relatively easy to tack (especially when sailing solo) and powerful enough (and a more advantageous PHRF rating). Also, a couple of year ago, I had the main recut - full length battens on top and upper mid, and shortened the foot length by 12 inches. The shorter foot length eased the weather helm and doesn't seem to affect performance. With hindsight, perhaps an 18 inch trim would be even better.
Re: Asymmetric - never tried one on our boat. My observations here on the river - where we mostly run down wind - is that a regular spinaker is better for a boat like the E33 - YMMV.
One more thought on running backstays - There was one other E33 (hull #1) here on the river for awhile that did have the running backstays. The owner previouslsailed on San Francisco Bay. AFAIK - he never used the running backstays here on the river, including racing.