Hitch mount rack and spare tire

I am looking to buy a hitch mount rack that will fit over the spare tire on my Jeep Liberty. Yakima will not fit unless I add a hitch extender and they do not recommend this. I am not sure if a Thule will fit ( no local dealers carry for me to try it). Allen makes a rack that they claim will go over the spare but once again they list no bolt to bolt length so I can't be assured it will fit. Since the rack has to be purchased online I want to make sure it will fit the Liberty before I spend the money. Does anyone have a hitch rack currently over a spare tire? Does anyone use a hitch extender with their rack? Thanks for the advice.

I have an Allen rack, but I don't have an external spare.

Is there a measurement that would be useful to you?

Perhaps distance from bolt to the vertical part of rack?

Yes that measurement would be helpful. I tried the 530 model and that does not work. Allen claims the 640 and the 740 models will ft over a spare. ( or maybe the numbers are 630 and 730 -- can not remember at this exact moment).