As I said, I have avoided any research and simply developed as with the old system.
The levels dropped once a part was designed, and within a few days jumped back up.
Areas I have not developed since the first week have stayed the same level. I noticed when a new part was designed, the research level also went down, but shot up days later and became higher than parts I haven't developed in weeks.
So based on what I have seen, I see no point in setting anyone on research.
This has allowed me to (as of testing) produce a Div 3 car that is currently lapping 2 seconds faster than 3rd place; and could slot into the top 10 of Div 1 using the same designer/drivers/staff as last year where I was nowhere. This is on stock parts.