I drilled my holes in the wrong position on my coat-of-plates plates, so I redrilled them lower, and cut the incorrect holes off.
Now the plates will only overlap by about 1/2", is that to little?
(I'm basing mine of Wisby 7, so it only has a few big plates.)

You could probbably get away with it, but for the sake of the small cost of the plates it may be worth replacing them. It also depends on what material you are using for the plates?

Ash

I don't think it's going to be an issue autenticity wise.
Most of these we only have the plates remaining so exactly how much overlap they had is just guesswork based on them being worn by an average sized man. Who's to say any one of the plate sets weren't for a smaller or far larger man, with or without thick padding under it. Or, though less likely in 1361 but not impossible... even a man in the first place.

Functionality wise it may even be better with minimum overlap as you get more coverage for weight ratio, unless you're going to actually use it for scientific weapon testing and you want several layers to absorb damage. If it's for sparring or re-enacting in general I don't see any reason to worry. Far more worrying in that case is the tayloring of the coat of plates to fit the body and not hinder movement. For that you may need to adjust plate shapes and/or positions to make it fit your body and not the original wearer back in 1361.
The one problem I can see with a lesser overlap is if the plates are now set crooked, or if the leather is too stretchy and the plates slide apart or catch the wrong way when moving in it.

By the way, here's a website with reproductions of all 25 Wisby armours from the Korsbeting ditch made by some friends of mine for the museum of Gotland for their "Kalla spår" (eng. Cold trail) exhibit.
These may give some pointers on fastening details and fit of plates as well as the shape of the shoulder cups of some of them.

http://www.hoashantverk.se/hantverk/hoas_rustningar/index.html

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Simple natural colors to the leathers and going for the practical utilitatian in look, these would have been worn by the comparatively rich and unusually well equipped Gjute peasant militia (some rich head farmers might have been closer to knights even) and the german mercenaries the Danes brought to do most of the fighting for them.
The same type could be made with any number of variations or embellishments of course if one wants to adapt them for more fancy noble use, say for a Danish knight or man at arms.


A detail of note is that the historians believe the militia split the coat of plates and the mailles available to them so everyone would be armoured to some degree when meeting the Danes. So above is how it would have looked at the battle of Wisby 1361, but under other circumstances the same combatant might have had a full maille under it, not just the gloves and cap. This also means that some of the coat of plates might have had larger cut outs for the armpits to facilitate a full range of movement with two handed weapons, there would be maille there to cover it after all so it didn't need to go all the way up there.
Having practiced and competed in very similar coat of plates for many years I know if you strap it on a little loose you get a lot more torso mobility that it looks like you could have in one of these. But the armpit cutout shape and size does make a difference for arm movement and shoulder rotation.

Made and fought in COPs for more than a decade, nearing two, and never had more than .5" overlap. I shoot for 3/8-1/4". Never had any issues. In fact I'd likely not exceed this much overlap, I do not think there is any real reason to bulk the weight up so much.

RPM

Thanks for the responses, very helpful.