Let's start with what prop are you running now? Brand and size. What speed are you getting @ 5300. You will need at least 2" of prop to get you down to about 4900-5k where you want to be. With my Scarab I ran a 23" and at 5k she was running low 60's(no GPS back then). But a 23" Mirage is way different than a 23" Quicksilver Elephant ear style or a...so lets try and not compare apples & oranges.
Yes a 26 will be too big for your setup. I amthinking a 23 mirage or maybe even a 21". Not sure how that would translate ina 4 blade B1.
Nick
1994 22' Classic-454 B1 Red & white
1981 13' Whaler sport(original owner)
South Tampa Bay, FL "May I mamoo dogface to the banana patch?"