I found SettingsSteel's post that I mentioned above:
http://forums.deeperblue.net/706264-post117.html
Sounds like he is using bungee as a significant portion of the spearline and really likes it. I'm wondering if that might make loading even easier & add a little extra range on the stretch?
I'm with azapa on the swivel/clips, I just removed mine from the RA as they make too much noise (I see the new RA's have a clear plastic sleeve/pipe over the clip presumably to avoid this and the scratching - or perhaps it's just used during shipping?). Worth trying though. I'm using a (double)
sheet bend, so that I can untie the spear quickly if necessary but the thin 6.3mm spear & MB recessed barb makeit very easy to pull the spear back through the fish.
....the big advantage of screw in rubber is that the rubbers axis and pull is exactly in line with the spear. The bulk rubber U, through the hole under the muzzle will have a down force on the spear as it is loaded and fired. Those hammerhead muzzles seem to address this issue quite well.
All in all the screwins seem to be a good idea to me.
It's not the screw-ins that give the straight pull, it's the muzzle design - RAs use bulk rubber but have a pull every bit as straight as any eurogun. You're right though, on the Omer XXV the bulk rubber will pull down - but that might be a good thing: the highly accurate Seatec Gabiano (ask Spaghetti how accurate it is) has a downward pull. Is it the wings on the Hammerheads you like? The XXV has a couple of mini wings but I think they are intended (only) for the screw-in rubbers.
With the railed Omer XXV Gold, I would have no concern about using the bulk rubber, as the rail will keep everything straight. My concern was specifically for the unrailed regular XXV, which I have. However, while playing with my spear guns last night I noticed a few tell tale scuffs about 10" along the barrel. While they might have been caused during loading, I suspect they are due to the spear scuffing the barrel during flight; if so, then the issue I was concerned about for bulk rubbers is already happening for screw-in rubbers & the overall impact is insignificant.
I'm lovin' the gun though. Still, need to see if the gun will stand the test of time: I noticed a surprisingly big gouge on the mech probably from when I lowered the gun while bagging a spider crab. I wonder if they don't use fibres to toughen their plastics as RA do?