If you're a beginner, there is a major reason that more than rough accuracy isn't necessary for deflections.

Deflections are just like mfg's suggested CG locations. Both are just safe starting points for products that are manufactured in large numbers. Most beginners think that there is magic to "the correct CG" location of their trainer. There isn't. There isn't just one special place for airplanes that are built to be overly stable by design. And throws for basically stable designs won't work with anywhere close to the accuracy you can use setting those throws.

Deflection meters are excellent tools. The guys who fly precision aerobatics can make very rewarding use of them. Of course, lots of those guys keep up with exactly what the throws are and what results those gave. And they test and change and record.

You know, if you're not the type that measures, records, tests, records test results and uses the info later, there is a good reason for you to save your money.