One thing I would mention, which applies more to the No1 MK III* than the No 4, is that a lot of the fine tuning on these rifles were specific to the rifle. By that I mean that the fit of the 3 barrel/wood points on the SMLE MK III, along with three two metal ones. (Barrel reinforce, pad before and after the inner band [Wood fits] the front nosecap to barrel, spring just to the rear of that and the inner band spring fit). In several of the written accounts of what they went through to make these guns shoot well in slow fire and rapid fire (Roberts comp) it is stated that a lot of the tuning was individual to gun.
Having examined a number of No4 rifles with central bedding, I can state that there is an art to where the pad is placed (1/3 of the way up from the barrel reinforce to under the middle band) on what distance and how the barrel compensates. Once again, based on the fact that the degree of hardness on No 4 action bodies varies somewhat, the draw pressure on these points seems to vary as well. It can be very frustration work, getting a rifle to group well with MK VII ammo at some distance. Of course with the near impossibility of getting shooting quantities of MK VII ammo these days, it really does not matter. All that I shoot these days, when I do is VIIZ or MKVIIIZ loads.
Lastly I would point out as competitive shooter and not a military user of these, that the front end bedding might be the best most reasonable method for service use, but when you add a US or Britishpattern sling and clinch it up tight, the center bedding on the No4 gives better results as regards group shift with varying sling pressures. I would much prefer to shoot a well regulated No4 center bedded than a front loaded No 4 if I have to use a sling.
Same is true of K31by the away, they shot very well with a front load of 1 KG and a wee bit of damping induced by the top barrel clamp and handguard (just snug). Try to use the sling as you would on an NRA course of fire and it gets a wee bit trickier.