[Ed_Dinning]

Hi Andy, possibly the best method would be to take all sec leads off both transformers and power them up. Do a winding by winding comparison and look for differences.
You should also look at the transformer primary magnetising (no load) currents and differences in heating. The clamp bolts you have used may not be sufficiently insulated from the core and ensure that the lams are butted together with a minimum of gaps.
Both of these will increase mag current and output volt drops.

Ed