What I referred to as "asymmetric" rigid parrel does keep the full length batten, and for anything much larger than Serenity I agree it might be structurally better than the D-former or Egg-former which surrounds the mast - also, I don't see any great advantage in symmetry.

Also, thanks for the reminder regarding downhauls. On my SJR and also Steve's: the bottom panel of Serenity called for a downhaul and so did mine, probably due to the geometry of the lowest sheetlet. I now have a standing downhaul on my boom (I just raise the sail until it becomes tight. I think Steve might be doing the same). As for the other panels - any downhaul would need to be adjustable, and probably not necessary for the set of the sail. However, downhauls would be a wise safety factor as David pointed out, and I forgot to mention. For convenience they might be in pairs, spanned.

So, it is not quite true to say that rigid parrels completely obviate the need for any other trimming lines, and I stand corrected.

There is, as David says, an interesting area for further development here - though it is not suggested it is a "magic bullet" - and while we know it works on a small boat, it remains to be seen how it would go on a larger sail.

(Personally, for a small coastal cruiser, I am more than happy with the spanned running parrel-downhaul arrangement which Slieve invented for his SJR designs).

Speaking of rigid parrels, this video clip from Steve D (Serenity) just came on Facebook today. https://www.facebook.com/share/v/1KR6WMqei3/

A sail with a planform which defies the rules of yard-angle/rig-balance yet sets perfectly, not a wrinkle, under halyard and mainsheet only. Rigid parrels do the rest. Nothing to adjust when reefing (except the halyard and the mainsheet).

History.  The origin of the rigid parrel goes back to around 2014 with the aerojunk (with its double wishbone) and the wingsail (with it's skeletal structure) which, in effect, do each amount to a form of rigid parrel to the mast. Then the "D-former" of Paul McK (see Feb 2021 magazine), which gave rise to the variant used here by Steve (July 2025 magazine), all based on the desire for a "symmetric" (same on both tacks) lug sail. And then came the asymmetric "pistol parrel" of Jan Cz. (see forum thread sorting out my parrels 10 November 2025) Then, more recently, Arne drew a refined version of an asymmetric rigid parrel, unpublished, which has not yet been tried. 

(By the way, note the slings which go underneath the sail catcher, which transfer the weight of the sail bundle to the lifts - without putting any load on the sail-catcher's skeleton. That's the way to do it. Steve has got things pretty tidy).