Dont take chances with your prior lab! I would say it is pretty difficult to screw up negative shots on the shooters end - but very easy, and likely, on the processing end. Especially in todays low volume film world, where many labs keep the chems far too long to squeeze out a few extra dollars. At your expense.
Send you slide film to either:
Denver Digital Imaging aka The Slide Printer www.theslideprinter.com
They specialize in E-6, and have a long history of good work, back to the 1970's. They use a dip and Dunk machine too, which is bber than roller transport (which can scratch your film).
North Coast Photo of Ken Rockwell fame/acclaim. Especially good if you want some decent scans at reasonable prices to go with your slides. They have decent volume too, due to the referral at Kens site.