Don’t think Ross is a hybrid of Canistel. Photos of this plant were sent by someone in the rarefruit yahoo group to a specialist in Pouterias – Pennington and he said it is a different species from P. campechiana. There was a thread about this some time ago. Ross is different from campechiana in that it fruits in clusters;P. campechiana fruits singly. Also the Ross fruits have longitudinal ridges which P. campechiana does not. Probably Ross is native to Costa Rica area as that is where Bill Whitman first got it. Ref: Oscar – Hawaii
Ross is distinctive among the others selections. The fruit are flattened like a hole-less doughnut and often is slightly fluted. The flesh is juicy and there are from 3 to 5 seeds in the fruit. The tree is slow growing and easy to control. Ref: Noris Ledesma – Florida