Ken,you mention you want the boat to be competitive.I don't know whether you are in a NAMBA or IMPBA area,but the dimensional requirements are different.Check with the hull manufacturer whether his boat meets the appropiate requirements.Generally boats that meet NAMBA dimensions are good in IMPBA,but IMPBA dimensions may not be OK in NAMBA.
Also the Classic Thunderboat class is larger than 1/8 scale,which is nitro powered.1/8 scales are about 42" long,while gas powered Thunderboats are 47" to about 52" long.
Harvey