See this page on the Dexter over/under kit for U bolt torque
http://l.b5z.net/i/u/6149609/f/Instruction_Sheets/059-551-00A.pdfThe bolts in that kit are 1/2-20 fine thread. I do not know what size U bolt you have.
The axle tube should have an arch in the middle of it. That is the axle camber. Looks like this. Don't mind the work boots. I did get my monies worth out of them...LOL
What size axles do you have? (load capacity) The larger the axle the more the issue "might" occur.
It is not beyond imagine that the leaf spring will be slightly twisted when the axle is unloaded. The spring is mounted on the axle seat and the axle has camber in it. This can put the spring at a slight angle and may make the hanger bolt go in hard. If you have a large adjustable wrench placing it on the spring and a little twist may help the bolt go in. Those that have U bolts rusted solid really do not have the easy option you used. Yours must be fairly new I take it to unloosen that easy. Mine where a bear to get off when I clanged axles.
Hope this helps,
John
