I used the asymmetric form of permanently-rigged sailcatcher, cut away on one side in way of the batten parrels, on Ivory Gull between 1995 - 2000, and there's a brief note about it in JRA NL 36, pp 23 - 24. I guess it stayed in use until she got a new suit of sails fairly recently.  It works. Whether it's worth the trouble of making it is another matter. I think it depends on the kind of usage of the vessel. A boat that lies idle all week and goes out for brief sails at the weekend will benefit from being able to zip it closed quickly and easily, in the manner of the bermudan equivalents. A boat that goes for long cruises, using the sail most days , covering the sail only when not cruising- not so much. Since I used this form of catcher on Ivory Gull, I experimented with lesser and lesser forms of it, coming down to simple cloth triangles fore and aft. These have some merit, catching the sail effectively without nipping it between small diameter line and spar; but on the whole, I get along quite well nowadays with simple spans of light line to catch the sail. There just isn't the SJR's problem of having to find a way to muzzle the jiblets, with any form of un-split rig.

Malliemac had a full length sailcatcher rigged on one side of the mast, when first rigged, and this was made possible because there were no batten parrels, just upper and lower luff parrels. This, however, is not a good way of rigging a sail, as there is insufficient control when hoisting and lowering. Malliemac now has batten parrels and an asymmetric catcher. 

There was an exchange on one of the threads a few months ago (I can't find which one) in which I had extolled the vertues of the McGalliard style sail catcher which suits the split junk rig so well - and it was contended that it won't work for an unsplit sail for reasons given that did not seem right to me. The working of the sail catcher has nothing to do with the split in the sail, of course.

Never the less, the system has been tried on a conventional rig and in at least one instance (I think it might have been FengZheng) had to be discarded because the batten parrels refused to slip down between the mast and the starboard tube of the sail catcher. Battens stacked up above the catcher and would not readily drop down into it.

One can't argue with a clear and real example, but since the split in the sail has nothing to do with it, it left me puzzled why the catcher works so well for the split rig. It finally dawned on me that both sides of the argument might be correct - that the reason it works on the SJR is because (according to the way Slieve set up the original rig) there are no fixed batten parrels, but instead, running parrel downhauls - and it may well be that their ability to unreeve a little is what allows the battens to drop down so nicely into the sail catcher.

The reason this is worth looking at is because (a) there might be someone with a conventional rig who can see the advantage of the McGalliard catcher (and although it may not suit some people, it does provide a way of instantly covering the furled sail and protecting from UV - and it does away with the need for conventional lazyjacks, requiring only a pair of fore lifts and a pair of aft lifts) and (b) because there are SJRs around now with conventional batten parrels whose owners might want to think twice before making a McGalliard sail catcher. (But the SJR does need something more than lazy jacks to muzzle - the jibs in particular take no notice of a lazyjack and slither all over the place - hence the particular advantage of the McGalliard catcher for a SJR rig).

Well, here is a possible compromise. I don't know how well it works, and this is pure speculation but the photograph below looks to me like a modified McGalliard sail catcher which has had a part removed, possibly in order to accommodate fixed batten parrels. You can see that its function as a UV protector is compromised, and it would not work so well for the jibs of a SJR - but it might work better than lazy jacks - at least on the port side anyway.

 I noticed it on the photos of the boat for sail on the "Askew 38ft 9in steel junk rigged schooner for sale, lying Cebu, Philippines, AUD $69,950" thread.

PS for anyone who might not quite understand how the McGalliard catcher is set up - the starboard tube of the sail catcher MUST run past the starboard side of the mast. Unintuitive as that may be you can NOT put both sides of the sail catcher down one side of the mast. In the above photo I think the starboard tube has simply been cut at the mast and the fore part left off. It really is a compromise, and may well have been a "plan B". It would be interesting to know.