Couch Quilt

I'm making a quilt as a wedding present to the couple getting married over Labor Day weekend. The bride chose a quilt she liked from photographs of quilts I've made.  Her favorite by far was one I made in 2000 for friends who live in Inverness, blues and greens and suggestive of nature, which is right up this couple's alley (see detail of quilt, below).

Last night, I finished the horizontal piecing--hurray!--and then had doubts. The groom is very tall.  The bride is also quite tall.

So I e-mailed Scott, the groom, who is beginning his residency in ER medicine at Duke University and about to get married and has a hurricane bearing down on him,  and asked how tall he is.  The answer arrived promptly this morning:  6'4".   The current version is 72" long.

My question: How long does a quilt have to be so that a 6'4" man can take a couch nap with his feet fully covered?