I've personally seen
Jim VH's tree and tasted one of the fruits.
The fruits seem to be as big as citrumelo (especially in this climate of the PNW where citrus fruits often do not grow as big).
The fruits have a terrible flavor, unedible. Although they look delicious and inviting before you taste them.
I provided a taste test description and another picture in this thread:
bounty of rare cold hardy citrus fruitshttp://tropicalfruitforum.com/index.php?topic=41558.0If it is a citrumelo, it seems to taste much worse than a Dunstan should taste. Maybe it could have been grown from a seedling from a Swingle?
Some of these rootstock varieties are often grown from seed. This one could have turned out to be one of the rarer seeds that was not nucellar, and so had a different phenotype.
The fruits seemed larger than any pictures of Troyer citrange I've ever seen.
And it's hard to be completely accurate or objective, but I do think I may have been able to taste a very slight grapefruit flavor to the fruits, although it was subtle. Although overall the flavor was definitely closer to orange than grapefruit. (That might not really mean anything, however)