Would a converter fit?

[Slowhand Bob]

Though some poo-poo the idea, I think Pietta is missing the boat by not reproducing the the small five shot .36 caliber Remington police(?) model.  This should easily be more popular than the equivalent '62 Colt version and would be a natural for a Kirst conversion, if five .38s could fit in the small cylinder?  My question is, what would be the minimum cylinder diameter that would be required to safely handle five .38cal rounds?  I do have access to a friends gun and could measure the cylinders diameter if I new.