I was at WDW first week of May last year and we watched Spectro from Frontierland and it was great!
There was only one Spectro that night at 9pm, we got to Frontierland to get seats at 8pm, but it really wasn't that crowded so we walked over to Splash Mountain....there was NO line. There was also NO line at BTMRR! We rode both rides twice...didn't even have to get off on BTMRR, just went again...and then we went to Pecos Bill's and got burgers and STILL found good seats! Now there were only two of us, so that made getting a spot easier, and we absolutely didn't cut or squish in. If you are a family of four or more it might be a little harder, but really we had no problems. We were just sitting down outside the gift shop next to Pecos Bill's when we saw the first signs of the parade coming down the street.
Don't forget, if the parade starts at 9pm, it ends up in Frontierland last, so you've got some time to find a seat even just right before 9pm. I don't think it really hits Frontierland til like 9:15pm.
Don't know if this plan would work in the summer or during a peak time, but for the 1st week of May it worked out great for us.