What version or brand of GT4 lip do you have? My Ridgeline GT4 lip had longer duct channels that tapered down to a 60mm OD. My 63mm Burkhart duct hoses fit over it perfectly. I've seen some V2 version lips that seem to have the ducts cut down shorter that makes the outlet larger and more oval.
I was concerned about the retention strength of just putting a hose clamp on the lip/duct joint and didn't want the hose to blow off the lip duct at 150+mph, so I took three tiny Allen bolts and nuts, drilled holes in the lip ducts about 5mm from the ends and 120° away from each other radially, inserted the Allen bolts from the inside of the duct and used locknuts from the outside to create a retention point for the clamp to pull on, like the rolled lip you might see on the ends of intercooler piping. Has worked great on track so far.
Random tangent: My biggest observation about the GT4 lip ducts are the direction they point in. The duct ends point outward toward the outside of the fender well, but the duct needs to go toward the inside of the fender well so you have this unnecessary tight bend in the hose that could have been straightened out and, in theory, should increase airflow and reduce turbulence/resistence. I dunno, just a thought I had while laying on my back staring up at the duct
