1st. a quick shout out to My friend Mort. Glad to hear you chime in here! BTW your not that old! but your farts do stink! Hope your doing better with the arthritis since i've seen you last.
Having raced / co skippered 4 seasons on an 85' E38 my assessment would be in complete unison to Slick470's. With the high aspect main it helps, but a well cut / condition main is a prerequisite. I also think Ericson mixed and matched the rigs on these boats? some with single profile spars (kenyons) and some with tapered spars (sparcraft blue labels) I think? There was allot off selling off of companies, aquasitions and mixing of spar parts in this era. The tapered spars IMO seeming to be more amenable to being bowed. Not BC of the taper but I think the Sparcraft extrusions might have had a little lighter wall thickness.
Knocking the sag out of the headstay, especially with high windage foils like curlers have, improves pointing and lets you control the slot better. For speed on this design I'd speculate to say the biggest advantage speed wise is probably being able to slack off when working off the wind. Having the ability to bag out a big ol %155 can really help pull in the right conditions. However If I were doing the kind of sailing that Christian is or going for long hauls I would ditch a hydraulic backstay so fast It'd be on the seabed before you could say hydraulic fluid leak. Yea its nice to have, yea its fun to play with, and it can be seriously effective, even essential on racing boats, but on a cruising rig I don't think the benefits outweigh the liabilities. A big part of the attraction of Hydraulic backstay adjusters is the ability to make speedy adjustments and their slow as a receeding glacier when compared to a split BS adjuster on tackle.
Serious cruisers on the other hand, require reliable, robust, and simple systems particularly in the standing rigging department, so, everything a hydraulic unit is not. An average gain of 1/10 th of a knot over a 14 day passage won't make up for the two weeks in port waiting to get the replacement parts. Lastly, despite what some may believe. The ability to slack off the BS at the end of the day does not necessarily benefit that boat in any way vs. having a fixed tension. It actually increases the number of stress cycles a hull goes through. It can actually propagate stress cracking, spidering and injudicious use has made for many a Keel smile. BTW I have a hydraulic adjuster on my boat and use it every time I go out (rebuilt twice BTW) but I use it conservatively. It takes allot of compression to get that gosh dern piece of alu-mini-ini-um to bend!
Ian.