More recent wind tunnel tests confirm the differences clothing can make. When Oliver Bridgewood tackled the one hour record a few months ago they demonstrated a lot of testing in the GCN videos leading up to that effort. Very relatable stuff since Ollie is a cycling enthusiast, not a pro. (Better than Ollie's previous aero demo videos with Cycling Weekly, possibly due to GCN having a bigger budget.)

While I wasn't ready for an off the rack skinsuit, let alone the custom job Ollie was fitted for, that series of videos did persuade me to get some snugger fitting sorta-aero jerseys and one of those rounded sorta-aero helmets (no fins, thanks). It helped. Cheap and easy fix.