I guess LN are not risking creating too many hostages to fortune with the very moderate knurling on the brass thumb nuts they have used - getting those tight may not be the easiest either.
Another variable (with screw head diameter and lumpiness in the case of finger tightening, or hex heads/screwdriver slots where tools are used - or the nutsaver which may not be a bad solution if it works well) that stands to significantly increase the available clamping force would be to use a finer pitch of thread on the stud. With the previously mentioned stronger stud material if needed.
There's another couple of potential issues that could quickly follow though. One is that the relatively short aluminium thread the studs screw into could easily strip - these casting grades of aluminium tend not to be the strongest ever. No designer will want to create a situation (by adding a screwdriver slot or hex head, or a fine pitch thread) where a clamping screw is easily done up tight enough for this to happen.
Another is that having the nut bear directly down on a slot as in the case of the LV skew rabbet and LN plough depth stops (without an intervening anti rotation pad) risks problems with it deforming as a result of the strips of metal each side of it bending/being pushed out sideways under the torque that gets applied by the thumb nut - unless that is they are thick and strong. (which broadly they are - relative to the thumb nuts used) This is a common problem elsewhere. It's not good that they are unmachined castings with irregular surfaces either. Neither is great engineering practice, but if done it's at least important that everything is flat/square/parallel and well finished in the clamping sandwich or the risk of problems will greatly increase and the grip and accuracy of alignment reduce. i.e. if the nut doesn't simultaneously touch down over the entire surface it will tend to disturb the stop setting as it tightens too.
Clamping surface area and finish are also big factors. It's best as above that the mating areas are accurately flat, and for example i wouldn't be keen on the way that the depth stop on the LV skew rabbet is powder coated either. Not given my experience of how slippery what's likely the same (polyester powder coating?) is on the jaws of the Mk 2 honing guide, and the likelihood that the cast and coated surface is in engineering terms probably quite lumpy. It's very likely that skimming/machining the clamping surfaces of the depth stops to make them accurately flat and parallel, and to expose bare metal would greatly improve the grip - although wear/galling/pick up could then become an eventual issue in the case of especially the cast aluminium LV stop.
It's not great practice either to have a screw threaded in a collar bear directly on a sliding rod as in the case of the LN plow plane. It risks marking the rod, the precision of location depends to a fair degree on the shape of the tip of the screw (tightening an irregularly tipped screw may cause movement), and the short aluminium thread that's only possible in the collar invites stripping with even moderate tightening.
Indirect locking with a split collar with a through clamping screw at right angles is a much better deal. This principle: http://www.bearingsrus.co.uk/single-split-shaft-collar - much as in a collet, but the collar in our case would likely be an integral part of the casting. The collar grips all around the rod/can be made longer if needed/can have lots of surface area so heavy tightening isn't needed, the hole can easily be made to an accurate diameter tolerance and surface finish, and the boss can be shaped so there's plenty of thread depth for the clamping screw.
A good quality dial gauge stand with accurately toleranced and well finished rods and inner clamp surfaces and decent sized hand knobs demonstrates these principles very nicely - it nips up really solidly with only moderate tightening of the knobs: http://www.machine-dro.co.uk/eclipse...tic-stand.html Not for nothing do they cost multiples of what a cheap one does...
The trouble is that the better arrangements tend to cost more. For all of the above there's not necessarily any absolute engineering rights or wrongs in this stuff - the task is to find a solution that works reliably and well at what is a fairly moderate price point, and simultaneously gives an acceptably long service life…