I borrowed these numbers from the @DukesTailgate twitter handle with respect to a potential Eastern Athletic Conference and researched some of
my own.

Their proposal

North
JMU 21,808 students $51.7M budget
ODU 24,176 students $44.2M budget
Marshall 9,593 students $30.6M budget
App State 19,280 students $36.9M budget
Charlotte 29,615 students $37.9M budget
Western Kentucky 24,492 students $30.5M budget
Middle Tennessee State 21.913 students, $35.3M budget

South
UAB students 22,080 $34.7M budget
Southern Miss 14,509 students $24.2M budget
Georgia Southern 20.418 students $31.6M budget
Coastal Carolina 10,479 students $36.4M budget
Troy 29,689 students $30.3M budget
Florida Atlantic 29.772 students $35.1M budget
Florida International 58,064 students, $36.1M budget

Others:
Georgia State 52,814 students $32M Budget
Ohio University 18,938 students $35.8M Budget
Delaware 24,120 students $44M budget

Another way to look at it

Average Distance Between Other Potential Members
Charlotte 385.1
Georgia State 406.9
App State 408.1
Georgia Southern 437.1
Coastal Carolina 468.7
UAB 473.0
Middle Tennessee 475.3
Marshall 493.9
Troy 508.2
WKU 509.0
JMU 520.5
Ohio 548.5
ODU 570.5
Southern Miss 650.8
Delaware 679.3
FAU 761.0
FIU 807.2

Number of Potential Conference Members within 300 miles (bus feasible)
Charlotte 6
JMU 6
Georgia State 5
App State 5
UAB 4
Marshall 4
Troy 4
Georgia Southern 3
Coastal Carolina 3
Middle Tennessee 3
ODU 3
WKU 2
Ohio 2
Delaware 2
Southern Miss 1
FAU 1
FIU 1