I've been looking into getting an SCHRS rating for the Isotope for a while, and have some questions/concerns. Using a tape measure, some published data, and some guesstimates, I've come up with a variety of potential ratings using the SCHRS calculator. Unfortunately, by using different assumptions/configurations, I get a very wide range of numbers. Clearly, SCHRS is not as straightforward as it's claimed to be.

For example, should the mast area be included in the mainsail area? The measurement instructions say that it should, but several popular boats listed in the official ratings table seemingly do not.

If I calculate mainsail area including the mast, and my current square-top mainsail, sailing single-handed, I wind up with a rating of 1.075. That's significantly faster than a Hobie 18. I'd owe a Hobie 16 nearly 6.5 minutes in an hour race. Under the Portsmouth Yardstick base DPN, A Hobie 18 owes me time, and I owe a Hobie 16 less than 1.5 minutes in an hour race. That's a huge discrepancy.

If I don't include the mast area, then my rating comes out around 1.098 - more realistic against a Hobie 18, but still way behind a Hobie 16 2-up. If I recalculate a Hobie 16 as 1-up, then it's handicap changes to 1.117, which translates to my owing it about 1 minute in an hour race. That seems more reasonable to me. SCHRS seems to place a large penalty on sailing single-handed.

If I were to do a lot of SCHRS racing, I think I'd make myself a high-aspect pin-top mainsail and race doublehanded. Then my rating would be 1.205 (omitting the mast area). That number would make me tough to beat.

Is there someone familiar with SCHRS measurement who can help walk me through the process, explain how other boats' numbers were generated, and get some Isotope ratings in place?

Regards,
Eric