I have the Sportworks Mod Series that is the same as Bolo's above. These are very good racks and i believe much better than racks that support the bike by the top tube.

They are heavy racks however, since they are so heavy duty. So the manufacturer limits them to two bikes on a 1.25" receiver. IOW, on a car you can only carry two bikes. I wouldn't use one of those adaptors because i think there is a reason that the manuf. has this limitation. It is probably too much tongue weight for a 1.25"

So if you MUST have four bikes then you will need one like the other rack posted here that holds the bikes by the top tube. Your bikes will probably move around a little more in the rack but I am sure plenty of people do it and get along ok.

So your best solution is to either put a receiver on from etrailer or call a local moving place like U-haul or a place that does hitch work. Camper dealers are a good place to check because a lot of them do this along with selling campers. (not much good to have a camper without a hitch.)

You will probably spend well over $200 if you pay someone to install it. I had one installed "profesionally" on one car and it cost me $240. The other car i just ordered it off etrailer and it cost me $80. Granted the $80 was a much easier install as my cirrus required dropping the exhaust etc.