I have the longest extended pin on a jayco with a short box 99 Superduty crewcab. My RV dealer said I didn't need the slider but I got the Reese anyway and the only time I have used it in 6 years was to try it out. I have parked it many times on places people said I could not get it in. They would gather and applaud after I parked it. I'm a pretty good judge of where I can back something. Grew up on a farm.
I think its more related to your skill and comfort with backing. I know how sharp I can turn without hitting the truck cab and I have never had to turn any sharper. I would make the decision based on my comfort level. I wish I would have saved the money, but for some it might be worth it.
1999 Ford F-350 XLT Crew Cab SB, SRW, V-10, 4.30 Limited Slip, Gear Vendors Under/Overdrive, Borla Headers & Exhaust, K&N Filter, BF Goodrich Velvet Ride Shackles , Turbowing, Power Programer, Amsoil By-Pass Oil Filtering System.