I also use the 1510 as carry on. It fits by D7000/Aquatica system, flat port, extension tube, two Ike 161s, two arms, three lenses (105, 60, 10-17) viewfinder, diopter, one Ike charger, one Nikpn charger... 42# all together!
I only check my large dome and another ike charger, and my focus lite etc.
I went hard case since I figure sooner or later, I"ll have to check it. Although the case appears smaller than 3/4 of the carry on I see now.