According to B&H:Size and weight ; the retro more equal to a 8x30.

SFL 8x30: 459g

Leica 7x35: 590g

SFL 8x40: 641g

So the 7x35 are much closer to the 8x40.

Length is:

SFL 8x30: 11.9cm

Leica 7x35: 13.2cm

SFL 8x40: 14.5cm

So the 7x35 are exactly in the middle.