LC - working with rpm

LC 2x28kg: 21/4min

OA LC 36kg: 5/5

LC 2x28kg: 16/4min

OA bar hang: 20sec/20sec

Tried two short sets with 28s at a higher than comfortable tempo; thus for 3 & 4min I end up at 5rpm. A long term goal (3, or 4, months?) is 10minutes at 4rpm. I already can do a 10min set, but at ca 3rpm.