Barry,
I've a pretty big mis-shapen (think Peter Doyle in Young Frankenstein) noggin' at 24"/61cm. Their XXL fits me better than the
Shoei St Cruz I normally wear.
The liner in the HCI is in fact EPS [Expanded Polystyrene (styrofoam)]. I'm betting the Shoei offers better protection.
If you plan to follow through with ordering, I suggest the second link I mentioned above, not the first. This will save you at least $20. You'll have to order by phone though. Make sure you talk to Mary. The first couple of folks I talked with didn't have a clue.
Regards,
Tom