I drive a stock 36 PD on a PD 17x54 hull and with around 100 lbs of chit, 10 gallons of gas and me (195) I get 29.8 on the gps in about a foot of water. I've had the same load plus 4 more people and still got on plane, took a little longer but I was satiisfied. I didnt have my gps that day to see top end.
i would think you'd get about the same on a light load but not sure on a heavy with a 48 hull. Maybe someone else will chime in on that.
And for the record, I haven't gps'd it in reverse

I might now for the hell of it.