This might be my most hair brained idea to date but it just might work. Below you will find the recommended method of calibrating a PG. My hair brained idea is, take the manufacturers amount of product per 1000 sq/ft and add it to the permagreen hopper. Note you should first run that product through the machine so there is some residual on the bottom of the "empty" hopper (see step 6). Add the recommended product for 1000 sq/ft, then park the machine on a large tarp, raise the sides to catch the product dispersed, run the machine up to 3500-3700 RPM's, open the gate for the recommended time it takes to cover 143' or 1000sq/ft (approximately 20 sec), weigh what you collected and adjust your rate dial accordingly. This way you are not experimenting in a parking lot or on yours or a customers lawn. 1 Verify that high RPMs are between 3,500-3,700. Adjust if necessary. 2 Mark off a test course of 143 feet. This represents 1000 sq. ft. of turf as you are effectively covering 7 feet with each pass. 3 Shift into High (H) gear, and time yourself over the course. Do the test several times to get an average elapsed time. 4 At 3,600 RPMs, the elapsed time should be approximately 20 seconds. In that time you want 1000 sq. ft. of granular product to fall through the hopper. 5 Using a postal scale, weigh 1,000 sq.ft. of product and add it to the hopper. 6 With the machine running, record the time it takes to empty the hopper. NOTE: the 1st test is not accurate because some of the fertilizer will be left in the bottom. Start recording with the second test. 7 If that time is less than your elapsed time, rotate the spreader rate dial (FIG. 6-1) to a lower number. If that time is longer than the elapsed time, select a higher number. Retest and adjust as needed. 8 After rate adjustment is complete, record your 1st, 2nd, and 3rd hole settings as measured with your calibration gage. Repeat the pattern distribution test and adjust if necessary. 9 Repeat the entire process for Low (L) gear.