The RC29V is the 'standard' 7X11 DD open-frame search coil.
The RC26 that you have has now been discontinued. It is the 5½X10 DD solid-body design.
The RC24 is the search coil that replaced the RC26 and is a 5X9½ DD that is an open-frame design.
The RC29V is the improved standard 7X11 DD that is designed similar to that used on the FORS CoRe or FORS Relic that has the rod-mount closer to center for better balance and feel. That said, I seldom used the standard coil on the Racer 2 as I find it to be front-heavy and more fatiguing, at least for me, When I hunt a more open sites and want to use that size coil, I grab my FORS CoRe most often. All my detectors, regardless of brand, keep a smaller to mid-size coil mounted because I search trashier places. The early mid-sized elliptical, the RC26 with the solid-body design, I preferred over the standard coil for most open-area searches. I kept a smaller-size 'OOR' or 5" DD attached to the detector most of the time since I hunt very trashy sites, but switch to a mid-sized coil for more open areas.
I let my solid 5½X10 DD go, the RC26, because I preferred the newer open-frame design and feel of the RC24 which is a 5X9½ size Double-D coil. The other coil you might ant to consider, if you decide to shop for a comfortable feeling and very nice performance afield search coil, is the round 7" Concentric. If you are going to be hunting a Civil War location, then also consider the terrain, vegetation growth, and be prepared for a place that was heavily used and might have a lot of trash to deal with. For the really dense debris sites I prefer the round 5" DD coil, and if the area is more or less an open condition with sparse targets to deal with, I prefer the 5X9½ DD open-frame or round 7" Concentric by-far over the other available factory coils for a Racer 2.
Monte