That's rolling the dice for sure. I do know it won't work without the proper spring. The spring is what holds the assembly in place.
I will say I have sat in the older style seat and I fish out of a 2016 PA with the Vantage ST seat. I personally think the older style seat is more comfortable. The Vantage ST seat has a gap between the base and the back of the seat and my tailbone sinks into this gap causing pressure on my lower back.
I purchased this seat pad and it has helped. OKWU COMFORT Waterproof Seat Cushion Pad with Free Non-Slip Cover Straps Carrying Handle Coccyx Car Office Chair Pressure Sore Relieving Wheelchair Memory Foam - Nurse and Therapists Recommended
https://www.amazon.com/dp/B013GPKFM8/re ... uEbGA1FC11If you do move forward with the Vantage ST seat and need one I have one for sale.