Things to look for:
Fish-eye
inssist the vendor sets it and keep it insured for life (high risk of chipping as it is likely to have shallow crown angle and very thin girdle)
The stone will look dark from close up
Plus side - it has a big spread
Otherwise, I''d be tremendously surprised to see those proportions actually worked somehow. There is a price for everything though, and I haven''t seen it. If you decide this is nice after seeing some more, good for you.
The size sounds more like 70 pts than 60. Could there be a .7cts cushion with more mainstream stats at comparable cost out there? I''d try.
My 2c
PS, about the spread: - something close may be feasible with more reasonable depth...
The current option:
weight: 0.59
depth: 50%
table: 69%
size: 5.5 x 4.86mm