How much hp will i miss out on if i choose to power up a 15a 15 d 1s flaffy? Thanx in advance

https://pokemongo.gamepress.gg/cpcalc#/

At level 30, an Ampharos with 15stamina IV will have 142 hp, 1stamina IV will have 132 hp.

Don't power up Flaafy, wait for the final moveset of Ampharos.