There are some photos of the Cutty Sark, pre-restoration, on the old SMML website:
http://smmlonline.com/reference/walkabouts/cutty_sark/cutty_sark.html
A couple of them show that the forefoot was a sharp angle with no curvature at all. The radius of the curve of the forefoot on the Revell model is about 7/16" in radius, or 3-1/2' in scale. This is not a huge radius, but it is not correct to the prototype.
Several years ago I did a comparison of the kit hull and the Campbell plans which included enlarging the drawings form 3/32" to 1/8"=1'-0" to match the kit scale. Aside from the forefoot issue mentioned above I found the following descrepancies:
The kit hull is about 1", or eight scale feet, shorter than shown in the plans.
The plans show six freeing ports in the bulwarks, the kit has five.
The plans show four small portholes at the bow, the kit has three.
The plans show a curved billboard or anchor lining, the kit’s is straight and vertical.
The ships stem on the Campbell plans is much more vertical than the stem on the kit. The difference is about 3 degrees.
Conversely, the angle of the bulwark at the stern, between the bottom and middle taff rails, is more vertical on the kit than in the plans.
The bulwarks are too short on the kit. The difference in the overall bulwark height is about 1/8 inch or one scale foot. Most of the error is in the lower iron portion of the bulwark which gives the already incorrectly numbered freeing parts a squashed appearance as well.
I have to say that I was very surprised to find that there were as many inaccuracies in this kit as there apparently are. I had always assumed that the kit was pretty accurate. Whether any of this matters is, of course, up to the individual modeler. Some of these issues are, for all practical purposes, unfixable while others can be corrected with varying degrees of effort. The bottom line is that if you build a Cutty Sark OOB, and do a competent job of assembly, painting and rigging, you will have a very impressive model that looks like a Cutty Sark. Personally, I love the old kit , hope to build at least one more, and I would like to try a Thermopylae conversion as well.
By the way, I did not say that I thought the Revell kit was in any way an accurate representation of the Thermoylae, only that the two ships were almost exactly the same size, and that the Revell kit has a rounded forefoot which is more correct for Themopylae than Cutty Sark. However, I could not help but notice in the photos posted of the Thermopylae model that she has three small portholes near her bow, which is another instance where the Revell kit is actually more correct for Thermopylae.