Any insert designed for dirt tyres is a big no no with carpet/astro style tyres as they are generally way too firm.
With dirt tyres the insert provides a lot of the support and shape of the carcass as the rubber is so soft. With carpet tyres the sidewalls are much stiffer and can generally support themselves pretty well, the inserts are only really there to keep the tyre up in the middle. With the firmer tyres inserts are also much less critical to get right, in general as long as they're 'close enough' you'll be fine
