What size jump/hardcore hardtail frame

I’m not off-roading at the moment due to work and weather, but thinking about stripping down my scruffy Mongoose hardtail as it’s not getting ridden much. And then building up a fun bike with the bits, as a project.

I was looking as the sub $100 frames on CRC: Da Bomb, Viper – they seem to be 15″ whereas I’m 5′ 11” and normally ride an 18″ XC frame).

Is 15″ right?

I’m 6ft 1″ and ride a 13″ commencal max max, length is more important than height on a DJ frame unless your wanting to fit a long post and ride about with the seat up.

6ft 3″ and used to ride a 14″ I’d say thats the size you’ll want!