I I have seen the Cushette...at Robbins in Delaware...it is a nice stone...the one I saw in person looked more square than rectangular...but the one on theur website...is more rect less square...hmmm...they person at the store didn't know much about it...or about modified squares at all...and he kept calling it coo-shette...trying to get over it unfortunate name...
So of the ones I am aware of...modified squares...I put into 2 basic catagories cushiony and 'squarer'
The cushiony ones are Regents and Cushettes
More Squarer are
Queen of Hearts
Lucere
Flanders
Dream
and the new one
I am affraid this brand does not publicize any 'optimal' measuremets for their stones. The one I saw looked 'sparkly' in an unusual way due to the particular cut used for the very small pavilion facets. The table was very large on the respective stone, but there is no way to know wether all are cut this way.
I believe Garry (Cut Nut) has inspected some of these. His impression is burried among older PS posts...