Just got a 1997 Bunton 52" hydro WB, 16 HP Vanguard. Will use a Proslide sulky with it, and want to mow at best possible speed. BUT, seems to me that max. speed is only aboout 4 MPH (I can walk about that fast) How to increase ground speed? has 6.50x13-6 tires on it now; if I went to 6.00x15-6 tires, would my top speed increase enough to make it worth while?