Way back in the beginning of the quest I brought up the point of lube volume and how I wanted to find a way to engineer a lube that was pretty much inconsiderate of groove count or capacity. How many years have we been reading of some CBA competitors getting the best groups by only filling the space above the gas check? I've seen that myself. It seems that filling all of the grooves, particularly with Loverin or multi-groove designs, adds too much of the slippery factor or possibly affects bullet balance by uneven jettison, especially at low velocity/low pressure. Most lubes seem to be too slippery and don't contain much in the way of things that can control the flow of oil and molten wax. Several years back I bought a grab-bag of stuff and got a couple sticks of LBT Blue Soft lube, and later Joe gave me a sample of his soap lube. Both of those lubes had the characteristic of shooting pretty much the same no matter how much or how little was used, or at least were far less sensitive than things like NRA 50/50 or Lithi-bee. The secret seems to be using components in the lube that allow it to be soft, yet not too slick. By a lengthy process of addition/elimination we started seeing trends in what does what and how all that works, and I at least concluded that lots of soap and using paraffin oils instead of napthenic (branched) oils lets us get soft lube that flings well yet resists extremely high pressure and isn't too slippery. Things made from "brightstock" base oils like most (not all) modern conventional engine oils, gear lubes, greases, etc. are death to accuracy, particularly if "too much" of a lube containing them is applied to the bullet. SL-68 and variants, LBT, and Joe's lube do the trick, though.
Sooooo, my prediction is that the extra capacity of those lube grooves won't matter with your SL-68B except for more atomized lube coming out of the muzzle. If you're curious, take a few and peel out all the lube from the front groove with a toothpick, shoot them along with the others that are fully lubed, and see what differences you observe. Shoot some clean cardboard at about a foot from the muzzle and observe the lube dispersion patterns with one and then two grooves filled. Try it again with the gas check version and see what happens.