Long story short, I'm doing German 1350's and 60's but I've fallen in love with breastplates. This wouldn't be a problem in case it was the covered one, but it's not. I've fallen for the non-covered breastplate usually seen in the 70's, 80's and transitional years (from what I can see).

"But Henrik", you say, "couldn't you just wear what you want?" and I guess, but I'm interested in historicity of things as well, and as such, I'm going to ask the members of the armoury on opinions on my solution.

Namely.

What if I simply put a surcoat or jupon on top? That would look pretty much just like any other rounded and covered defense worn underneath a garment, would it not?

Now the reason for going with the uncovered cuirass rather than the covered one is that a. I do like the look and for less historical settings (or whenever I don't have my helmet), I can wear it openly, whilst when in complete armour I can lace a surcoat over my torso or button a jupon over it (until, one day, I get a different helmet).

Do you find this a downright stupid plan? Is it understandable and something I should go for? Or do I just bitw the bullet and get the covered breastplate for my 50's kit and eventually get a non-covered for a 70's to 1420's one?

What the rest of your kit looks like? Do you have some pictures? If everything fits with the late breastplate except the helmet, buy the breast and eventually another helmet. It's easier to change helmets than breastplate on an event...