[Johnny#5]

Any straight he could make on the river would require that he make a low on sixth which he would raise. The only exception is a broadway, which makes no sense given his 5th street checkraise unless he has exactly AcQc, so we can all but eliminate a straight for him here.

A flush is definitely possible here and I assume he would raise the river with a flush and we would have to pay off. So if we bet we lose one extra bet if he makes a flush. The fact that he just called 6th instead of raising means he has to have some sort of made hand unless he has 9cxc or Qcxc, which is unlikely. So let's say he'll make a flush 5% of the time (seems reasonable.) And let's say he'll make KKK or AAA another 5% of the time. The other 90% of the time he'll either raise with a low or fold/call with a worse high hand. If he makes a low we chop and the raise doesn't cost us anything so we need him to call with a worse high about 10% of the time in order to break even.

So it boils down to will he make a crycall with kings up or aces up getting 11:1 or so. I think he will have this hand over 10% of the time on the river here and you can usually expect a call from people hoping for whatever. Maybe not though. I could be convinced otherwise.