I HAVE FOUND THAT THE HT-100 CARBON FIBER DRAG WASHERS AND THE METAL DRAG WASHERS FOR THE PENN 49 REEL ARE ALMOST A PERFECT MATCH FOR THE NEWELL 500 SERIES REELS. YOU WOULD ONLY HAVE TO REMOVE A VERY SMALL AMOUNT TO REDUCE THE OUTSIDE DIAMETER OF THE DRAG WASHERS TO HAVE THEM FIT PERFECTLY. TRY IT YOU'LL LIKE IT!
Try Bryan Young's 5+1 carbontex drag system for the 500 series. More drag and smoother. I also used to tweek the HT-100's for the 500/600's but no longer have to with Bryan's system. The 600's use a 7+1 drag system...mucho more drag :o