SAME body on the Stradic 4000 & 5000. Spool depth is the main difference. Well slight larger diameter on the 5000, but its less than 1/16" of an inch.
I swapped a spool w/ another guy and found this out. :P
I use the 8000 Spheros on my 9' rod, but the 5000, or 6000 would work as well. It is more the weight to balance the outfit rather than the physical size for me. I went w/ the Spheros because of the waterproof drag.
Both are good reels. The Stradic is SMOOOTHER for sure & comes w/ 2 spools. Can't go wrong w/ either reel.
Which Slammer are you using the 460, or 560?