BET rootstocks can be kept at that height but you will have to fight it to keep it that small. Every winter you will want to cut the top out and bend branches to force it to slow down growing straight up. An asian pear runts most trees but not BET it can grow several feet a year (sometimes 8 - 10 feet per year). They are susceptible to fireblight. All that bad i said about them sounds like someone who doesn’t have hundreds of them growing like i do. They are very strong rootstocks. Here is what you are getting into.