I would agree that the body design is much more similar to the Morse than anything else (shape, size and wood type). From my experience, I would say that the neck is not all that different than the Silhouette Special with the exception of the black paint.
I used my SUB1 again last night at a gig for a set. It makes a great backup axe, and I am definitely finding more appreciation for it after gigging with it a few times.
The Sub 1 body is identical in size and shape to the Silhouette Special body. Sans the relieved areas (body sculpting) and the fancy paint. The Morse body may also be the same, I have never seen a Morse in person. It probably looks more like a Morse due to the lack of sculpting on the horns.
Additionally, a Silo Spec pickguard fits a Sub 1 perfectly.
The Morse body is 1/4 inch wider than the others, as confirmed on this EBMM website in the specs. It may be the same length, but I doubt it. Can't tell as EBMM doesn't list body length as a spec. I would think the Morse body (not Y2D) is slightly longer than the others, because of the pup arrangement. Without a doubt the Sub 1 body is EXACTLY the same dimensions as a Silhouette Special, this is 100% confirmed fact my friends. And the Silhouette Special neck profile is most likely identical as well, and in my experience feels exactly the same. And I've played a few Silo Specs.
Because the Silhouette has a 24 fret neck I would think the body might be a tad shorter than the others, because the total guitar length is the same as the Sub 1 and Silhouette Special. Or the body is the same length and the neck is set-into the body a tad deeper. The Morse overall guitar length is 1/4 inch longer than the others (see the specs) and this is due to body length I presume.
Give this some thought, investigation, and look at the specifications on this website in the Instruments section.....
Sub 1 - Size:12-1/4" wide, 1-3/4" thick, 36-1/2" long (31.2 cm wide, 4.5 cm thick, 92.7 cm long)
Steve Morse - Size:12-1/2" wide, 1-3/4" thick, 36-7/8" long (31.8 cm wide, 4.5 cm thick, 93.7 cm long)
Silo Special - Size:12-1/4" wide, 1-3/4" thick, 36-1/2" long (31.2 cm wide, 4.5 cm thick, 92.7 cm long)
Silhouette - Size:12-1/4" wide, 1-3/4" thick, 36-1/2" long (31.2 cm wide, 4.5 cm thick, 92.7 cm long)
The Sub 1 and the Steve Morse bodies are made of poplar. The Silo and Silo Spec are alder. Thus the Sub 1 may have body resonance and weight similar to the Steve Morse.
I own all 3, Morse, Sub, Silo Special. After a brief comparison. The sub is most like Silo special, just without the body contours. The Morse is wider and longer, and actually has a less rounded edge to the body, than the Sub.
I own a Morse and a SUB. The SUB has a smaller and lighter body. But there is really no problem for adjusting between the two.
The weight difference is the main aspect.