Mine is a D5 standard not XL. I picked up the enlarger and accessories and I was correct that the carrier plates slide inside the speed carrier frame... basically the speed carrier frame fits the negative stage the same as the later D series negative carriers that have the rectangular frame bevel on the base side then it has a slot where you fit the actual negative carrier inside of it so you can swap out negatives without lifting the head off the negative stage. In theory it would probably work well but the ones I have (two speed carrier frames) both have significant light leaks. I ended up working a deal with an eBay seller and bought 35mm, 645, 6x6, 6x7, and 4x5 omega carriers for a bundle price and there are no light leaks with those inserted. Thanks for replying to this old thread guys!