Is it ok to raise the seat up some to tighten it? I really don't want to put her in a booster but I am short on vehicles I like and can afford.
No, you can't raise the seat to tighten it up based on my re-reading of my manual just now and the way I understand it. You could always call GM/Saturn to double check though? The reasoning behind reclining is to prevent contact between the vehicle head restraint and the child restraint, so one would think it would be ok to have it more upright if there was no contact with the head restraint with it being more upright. I have no experience with the regent to comment on that, and I would NOT be comfortable putting the seatback upright without talking to GM about it first.
How does the regent SBP compare to installing a Radian? The Radian is compatible with the seatbelt, it just takes some effort.
Here's the page from the manual with the wording:
http://i5.photobucket.com/albums/y194/snowbird25ca/Carseats 2/DSC00415.jpg
Are you trying to install it on the passenger or driver side? The buckle stalks are fixed in all positions, but I suspect there is a slight width difference in the spacing between passenger and driver, so maybe one side would work better than the other? The best trick with the seatbelts in there with the radian is to unbuckle and let a little bit of seatbelt go back into the retractor then re-buckle it.
The LATCH limit on the vehicle is 48lbs - would that give you some more time in the Regent?