Greg,
Although my best times are as shown in my sig (sea level, 55 Deg), in the normal summer temps (85F) and mid life tires (100 passes), 1.275 is more typical.

Phoenix 12.2 x 31.25 W, 31.8" tall, published weight 33 lbs, plus inner tube ~9 lbs
The sig was 4.30 gears, this year 4.10, but I don't see any significant difference (just like when I put 4.56 in it when the 4.30 broke). In the beginning of this year, with 4.10 gears and 193 passes on the old slicks it did 1.241 at 57 Deg air temp (30.02"Hg good air) with a 9.18 ET.
And 26" front tires for rollout comparison.

I have thought about trying a M/T 10.5W tire, but I doubt I would get the 200+ passes on a set at 3250 lbs like I do now with the larger tire. So cost would go way up, even if it works.