Just removing a shim or two is dangerous (not wise maybe a better term) as not all Angels leave the factory with the same amount of shims, they are set up to be the "correct" pressure using what needs to be added. the LPR figures given as stock are the ones that are known to work with the minimum of faults. If you want to further extend the use of the gas source and in some cases changing things to be more "gentle" on paint you move the LPR settings. With a Preset you cannot do this at all. Presets vary greatly even within the same maker so you can't say "oh I have set the LPR with an adjustable and then I hooked up my LP preset and it read XXXpsi so this make of LP preset gives XXXpsi as a reading" This is due the varience between presets.
Effectively I run my adjustable in the regular setting procedure for the Angel as it (the adjustable) is set at 350psi so I don't move anything. LPR's can and do go bad and springs (shims) get tired and unless you can check this accurately then you are pissing in the wind.
As I said before you use a preset if you are never going to adjust a thing...if this isn't the case you buy an adjustable.
But how many users of presets especially those with Angels move the LPR settings and then bleat about things not working correctly. I will never use a preset unless I have to ie sponsored to do so or a marker given to me to use has one attached.
The input procedure for checking the LPR is the minireg adjuster screw is flush and 350psi is inputted to the minireg and then the LPR reading is then taken ...so this is 350psi before the minireg....the work around would be to remove your minireg hook up an AA Guardian and check the output pressure and fiddle until you get 350psi (as with the adjuster screw flush it make the minireg basically a gas through)..starting to get expensive now isn't it
So if this is what you want to do(check things) then you need an adjustable.
Market forces nothing else is what has prompted WDP to sell the preset...and even that was a rebadged item and now a newer one (different maker??) is getting released.
In an ideal world I'm sure WDP would love to continue selling just the AIR but it is expensive and that puts it out of a lot of peoples reach so rather than have people use another make of regulator then WDP introduced the Preset badged for them.
Why do you think they changed the threads on the ASA mid production on the LED...as people were wanting to use their previous favourite regulator in the miniregs place and if they couldn't do so they (WDP) would continue to lose sales..they changed it and the sales continued