Isn't it pretty much standard to measure from foot to eyes now? And has been for a while?
Anyway, I painted a bunch of Khurasan late16th/early17th century cuirassiers along with a bunch of By Fire and Sword figures. The Khurasan ones are maybe a wee bit more 'buff', but mix well with any 15mm range I can think of.
The bottom line is this: Khurasan make great 15mm figures. Really, really pretty stuff. And the ones I worked with are along the lines of most other modern 15mm manufacturers. Now if the late 14th century range is a bit taller - that's OK. It will mix OK once it's painted. It's not like Testudo's minis are massively larger than other comparable miniatures ranges. So I'd say - get some Khurasan figures. I'm rather sure you'll like them.