To work with a multiplier on top they have to be rung for a multiplier. The usual argument about fixed spool reels is that they need big rings to reduce the friction of the supposed huge coils of line that come of the reel. Put a sensible line on a fixed spool reel though and watch it during the cast on a multiplier rod and the loops will have disappeared long before they get to the 1st ring. The blank, the line and the caster are the things that make a difference.
No doubt manufacturers will do their utmost to convince us that we must have the latest and greatest in between or what ever rings to get the best cast but having always used a fixed spool reel on a multiplier rod they will have great difficulty convincing me that it will make any noticeable difference. I went down this path because decent fixed spool rods were not available when I started sea fishing. It was also very clear that the fixed spool rods on offer were very under ringed - why? to recoup the cost of the reel seat. The blanks were the same. On that basis I would always recommend that people should buy multiplier rods if they ever intend to use or try a multiplier. Mounting fixed spool reels on them was a problem but it isn't an issue with sliding reel seats. Many of these hold a fixed spool reel more reliably than some multipliers.
i agree get rod rung right to take both types of reel:just as imex have done with ther new ceps range of rods:clap3: :kissing: :clap3: if yer fishing no proplem ,if yer in a casting comp where inches matter ring it for a multi as yer fine tuning your rod as you would your reel.