towing an ultra light, mini camping trailer ?

I wouldn't use overdrive

yes.

Are you talking about this trailer? http://casitatraveltrailers.com/patriot-deluxe-13/

Look, it's your decision, and I'm sorry to tell you this, but, you're making a big mistake here. The car you're talking about only has a maximum tow capacity of 1,000 pounds and this trailer far exceeds that . Here's a link to the specs on your car, http://www.edmunds.com/buick/regal/2003/

Also, as I stated above, the hitch or tongue weight is 245 pounds! I wouldn't even attempt this with my Subaru Outback and it's rated for towing up to 2,700 pounds. Again, it's not just the total weight but, where it occurs and my limit on the tongue is around 200 pounds. So, you're taking a enormous risk here and in re-reading your post you're thinking of taking this across country? This is not only not a good idea, but, DANGEROUS! You have the wrong vehicle for this purpose. I suggest you take a closer look and replace your vehicle. Who may I ask suggested to you that your car was appropriate for the Casita?

Penny, by the way, the average rule of thumb is the hitch or tongue weight is 10 percent of the tow capacity weight, so, if your car was rated for 1,000 pounds, that's 100 pounds. Don't know how old or what earlier models Casita made with a lighter tongue weight, but, the smallest model they have on their website is a tongue weight of 245 pounds. And, even though I might just be able to do this on my Subaru, there's no way you can do that on the Buick. Did you purchase the Casita used? I like the these trailers. But, paired with a sedan like your car is not an appropriate match, sorry. You'll thank me for telling you the truth.

I have towed a loaded U Haul trailer at 990 pounds with my 2013 Chevrolet Impala. It's rated for 1000 pounds only with 100 pound tongue weight. Empty weight is 990 pounds. Loaded, it was 1500 pounds with 156 pound tongue weight. It tows nicely and I drove up Lewiston Grade on US 95 at 65 mph. Passed many solo cars along the way. It's powered by a Cadillac 3.6L V-6 (217 CID).

In fact, I made 3 one way trips with my rental U Haul trailer from Los Angeles to Seattle. Taking various routes. Such as US 395. Or I-15, US 93, and I-90. I even passed through Montana one time. 2 roundtrip travels from Seattle to LA and back with U Haul trailer in tow with my 2013 Chevrolet. Just obey the speed limit. 50 mph break in period for the first 500 miles. After that, just obey the posted speed limit. Did fine at 75 mph. However, I suggest keeping the speed low at 65 mph or lower. Obey speed limit 100%!

I recall the 2003 Buick Regal is a bit different in speed. 50 mph for first 500 miles and 55 mph thereafter. 2003 Buick Regal has a permanent speed limit of 55 mph after 500 miles. Mine is 50 mph for first 500 miles. Unlimited after 500 miles. Try to avoid using overdrive is all. I tow using both overdrive and drive. I prefer drive on my 6 speed automatic. 5 is preferred. Drive is okay! D is Overdrive.

If you are determined to use this car to tow your trailer I would look at installing heavy duty shocks and springs in the rear. Power will not be an issue with the 3.8 V6 but the weight could be. I would also want to have trailer brakes for safe stopping distances. In any case don't exceed 55 mph.

Since it is a travel trailer, I suspect you will be towing it several times over the next few years. The tongue weight does not bother me that much as an example, 2 people in the back seat that weight 200# would be equal to the 100-150 tongue weight. I would strongly recommend an auxilary transmission cooler. especially if you live or plan on traveling to places that the ambient temp is above 80F. Heat kills transmissions and that camper will put an extra load on the transmission.