I wouldn't do it with my soft top. I got a Congo Cage and just the cage by itself wasn't that bad. I put up to 4 kayaks up there and hauled them form MA to FL back to MA and then to ME last summer. No issues. The weight you are talking about on top of the soft top bows is pretty heavy for the size of the bow.
Participate in life....Keep movin'....Go there....JK'n it.........Do it! Jeep #1: Red Rock 08 JK Rubicon 4dr, 6 sp manual, Stock Mud Tires, MyGIG Upgrade, Hard Top, after sale BestTop SunRider Soft Top, Congo Cage Rack, Mopar slush mats Jeep #2 Black 08 JK Rubicon 2dr, 6 sp manual, both tops, some chrome...uggg (my wife's jeep) Jeep #3 White 92 YJ (my son's jeep) A great quote from a good friend: "All hail click clack and master jk'n." Click and clack are my idols!