The world's earliest go-bar decks were caves where the craftsman used sticks from the ceiling of the cave to the work piece which was positioned on a BFR (big &*^%^ rock). With this said you can see that the "utility" of the deck, since this method worked, exceeded the accuracy of the deck. For a go-bar deck a high degree of accuracy is not important. You can shim things if it bothers you. What is important is that your dishes are accurate and supported well enough so that the cumulative force of many go bars does not change the domes.
As for the bench - I built my first ten guitars on a stinkin
rolling kitchen cart in a unused bathroom........ It worked for me and I had never even seen a proper work bench so I didn't know any better.As Rod indicated some jigs and fixtures do need to be dead-nuts accurate with a good example being what you use to slot a saddle and/or how you cut your binding channels, cut rosette channels, etc. But IMHO one of the beauty of the go-bar deck is that the go-bars themselves counter inaccuracies to a great degree so long as your work piece is well supported and true.
A word about domes on guitars - no mater what degree of accuracy we build into our domes the domes on a guitar are dynamic - they will change and rise and fall with humidity, string tension, etc. I build my tops to 25' but depending on my bracing and the spring-back of the top itself I seriously doubt if my finished tops are 25'. My bridges are pre-radiused to 25' and sometimes when I trial fit a bridge it will require sanding on the guitar top in it's relative position to fit well. Sometimes the bridges will require very little if any sanding to fit well. This tells me that my domes are not always 25'.
Our neck angles are corrected with flossing the cheeks to set the neck angle correctly relative to the bridge height and position. So what I am trying to say here is that building with a high degree of accuracy is important, certainly so, but.... we also will be doing many things to custom fit the guitar's component parts for a precise level of fit and performance. And in my view this is all part of what it takes to build a guitar and expected.
So don't agonize over the accuracy of your go-bar deck or jigs if they will do the job well enough and you will find ways to increase the accuracy of how you build, many of which will be required anyway, as you get into the actual building of the guitar.
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