In answer to your questions
CoElkHunter:
CZ 550 have had zero, one, or two cross bolts rather unpredictably (from an outsider perspective) over the last couple years. Apparently the single (or third) cross bolt behind the tang area may have been a reaction to some stocks splitting under recoil because the tang area was not relieved enough in some factory runs, but the traditional (and rational) location for the two cross bolts is as previously stated, and where they are on this particular .416 Rigby: the front cross bolt should be immediately to the rear of the action front recoil lug, and the rear cross bolt should typically be at the rear of the magazine, between the magazine and the trigger mechanism. Preventing a crack at the wrist is not accomplished by way of adding a third cross bolt there, it is accomplished by relieving the stock (i.e. leaving a visible gap behind the rear tang) to ensure that the recoil is absorbed by the front recoil lug rather than the rear action screw. Truth be told, I suspect that only one cross bolt behind the front recoil lug is all that is needed... All of this is moot with a synthetic stock that includes a full length aluminum bedding block (the Bell & Carlson stock sold as the CZ Aramid stock or the B&C brand is truly awesome in that - and may other - regard). Unless you love walnut, do not think twice, add a B&C stock for $290 and you will never have a stock issue...
As discussed in other posts, it seems pretty objective to state that some CZ 550 series are pretty clean from the factory (my .375 H&H was, and apparently so was your .458 Win) and some are not (my .416 Rigby was not). I suspect that it has to do with how sharp the cutting tools were the day an action was made, and whether a particular rifle was produced with fresh cutting tools (clean smooth cuts, no burrs, etc.) or with end-of-life cutting tools (machining marks, burrs, etc.). You see clean and not so clean CZ 550 throughout the years of production. If there was a seemingly "turning-point," it was when they decided to move from the Brno ZKK branding to the CZ branding, sometime during the 1990's / early 2000's if memory serves. I generally agree that the ZKK series were generally more consistent (my earlier ZKK 602 .375 H&H and ZKK 601 7x64 were OK) and I suspect that they had a manual deburring step in the production then, which they clearly do not have anymore otherwise some obvious burrs would not make it to the market. It is a shame, if you ask me, and a rather stupid minor cost-savings decision that likely is costing them major revenue loss because it gave rise to the "CZ are crap" internet legend...
The .416 Rigby is by far the best .416 cartridge out there. Its cavernous capacity allows it to be loaded at very low pressures for typical .416 performance, which has been historically good enough, and which the 416 Taylor, .416 Hoffman, .416 Rem, .416 Ruger, and many others all duplicate but at higher pressure. OR, the .416 Rigby can be hot loaded at .416 Weatherby (which is nothing but a .416 Rigby shell with a belt) level, into a different dimension of performance ... and recoil (there ain't no free lunch, right?)...
In terms of recoil, the typical .458 Win. Mag. 500 gr load at 2,100 fps in a 10 lbs. rifle produces about 55 ft/lbs of free recoil. The .416 Taylor pushing a 400 gr slug at 2,300 fps from a 10 lbs. rifle produces about 48 ft/lbs; and the .416 Rigby shooting the same 400 gr load at 2,400 fps will produce in a 10 lbs. rifle about 58 ft/lbs of recoil. In so many words, there is not a whole lot of difference. The lighter bullet recoil is offset by the higher velocity recoil. For comparison, the .416 Wby pushes that same 400 slug at 2,700 fps with 83 ft/lbs of recoil from a 10 lbs. rifle. You can get the .416 Rigby up there if you want, but you will remember the first time you pull the trigger on that load...
.416 Taylor vs. .416 Rigby? Same difference if you load at historic Rigby levels... The Taylor is more compact and can be chambered in a "standard length" Mauser 98 action. The .416 Rigby requires a true magnum length action. The Taylor operates at significantly higher pressure. This used to be a meaningful argument in the days or cordite. It is essentially an obsolete argument with fundamentally temperature-stable modern propellants. Ah, but the romance of the Rigby, Robert Ruark and Harry Selby! Yes, but only to those who care about it... Objectively, the Taylor is less versatile because it is already loaded to its absolute maximum powder capacity. The Rigby leaves you a lot of room to play and up the velocity if it is of interest to you. Beware though, that for every 10% increase in velocity, the price to pay is a 20% increase in recoil... Another consideration for those who do not roll their own, is that there is plenty of factory ammo for the Rigby, even in Africa. Good luck with the Taylor, even in the US, on that front...
I hope this all helps