Wave drag of a Sears-Haack Body

[Kryptid]

I've been doing some work on an original aircraft design. As part of the feasibility process, I decided to try calculating the wave drag of a Sears-Haack body with a length of 49.2 feet (15 meters) and a fineness ratio of 14 (a recommendation given by Dr. Raymer's aircraft design book). This results in a maximum radius of 1.76 feet (0.54 meters). I used an equation I found on Wikipedia to calculate wave drag at Mach 1 at 36,000 feet. The result I got seemed unreasonably low, however: about 186.5 pounds of force (829.6 newtons). Granted, this is a very skinny object compared to just about any existing airplane, but that drag force still seems awfully small. There were two equivalent forms of the equation and both of them give this same answer. Unfortunately, Wikipedia doesn't cite a source for where it got its equation.

Does this seem wrong to anyone else?

Here is the math in case anyone wants to check over it:

Here are the calculations to find the volume of the Sears-Haack body:

Volume = ((3 x pi^2)/16) x maximum radius^2 x length
Volume = ((3 x pi^2)/16) x 1.76 feet^2 x 49.2 feet
Volume = 282 cubic feet

These are the calculations to find the drag force at Mach 1 at 36,000 feet (660 miles per hour/968 feet per second)

Wave drag = ((64 x Volume^2)/(pi x Length^4)) x air density x velocity^2
Wave drag = ((64 x 282 cubic feet^2)/(pi x 49.2 feet^4)) x 0.00072 slugs/cubic feet x 968 feet per second^2
Wave drag = 186.5 pounds

I saw in Raymer's design book that slugs per cubic foot are the go-to measurement for air density when using imperial units. Should I have used pounds per cubic foot instead?