Compressed powder or not is irrelevant.
Lots of data is compressing powder.
Plated bullets are usually designed to stay under about 1,200fps, give or take.
Generally, start at starting loads for equivalent weight jacketed bullets and work up to mid-level loads or loads that reasonably indicate 1,200-ish fps for your barrel length.
In other words, if max data is showing 1,350fps and start data show 1,050, you'd want to be at about mid-level data since velocity increases are reasonably linear.
Having a chronograph helps a lot, so you actually know the fps and because your barrel length may not match the official data.