Quite a varied size range. If his is 16” then he has one of the big two, Rita rita or Rita sacerdotum both of which are supposed to reach 1.5 m or more. But I find it interesting that many are said to reach around the size your fellow hobbyist is encountering. I have never seen a large one in the flesh although finding smaller ones here in the UK is also VERY difficult. It may of course be that he has a type little known about.