Concentric only squats

I always did parallel squts and can do good weight but im able to go all way down to deep squat (so called ass to grass) when my feets are in shoulder width without any problem.
The thing is that im much weaker in start position to parallel of deep squat (ATG).
I would like to spend some time improving my deep squat, so im thinking of best way to doei it.
For strting strength and RFD always was good to do concentric only squats (Anderson dead squat, press from pins start position), is it good to go with weight that i can do 15 singles to failure or 1 in reserve every 30 sec. for 1 single for little bit of growth and strength, progress 1 rep every sesson untill reach 20 reps then add weight ?
Second option is to do half reps from bottom to parallel, what are your thoughts and expirience on this?

Current squat max?
Normal working weight?

Prallel squat eccentric/concentric 236 kg with 1.5/2 sec. eccentric and my deep squat is much below that with sme set up, problem is from the start to parallel have hard time to transfer from eccentric to concentric and muve weight up to prallel position.

Id suggest some box squatting
Or pause squats.