Hi... I have had the Honwave 3.8 air floor for three years.
I started with a Mariner 15 hp 2 stroke and moved up to a Yam 20 d 2 stroke.
On a flat calm, the engine runs out of puff before the boat feels challenged.
Here are some of my ownership notes on the thing, I never had or considered the Honwave 4.0 with the rigid floor. There are a lot of posts on here regarding the Honwave 3.8 - just search on those words.
1) Buy the launching wheels - they are a bespoke item and not cheap but very very worth it.
2) My only time when I loaded the boat into the back of my landrover, with the engine and all the rest of the stuff, I almost passed out after 15 minutes from the petrol fumes from the tank. Just as bad with the tank empty as full.
In my opinion, boats and fuel belong on trailers not inside cars
3) The boat gets a decent enough V shape in the hull when the floor is inflated BUT in a moderate chop it is still very uncomfortable unless you are dawdling along.
4) Its very sensitive to trim. I dont sit on the stupid bench they provide, at the speed I want to go I want to sit IN the boat not ON it. So shuffling my position in the boat affects the trim dramatically. The floor flexes upwards when you get on the plane and does react to the changes in speed.
5) Unless you tie everything up in your boat, all your stuff will all inevitabley gather in the centre seam that joins the two air chambers in the centre of the floor.
6) Glue four extra retaining loops to the floor around the existing tank tie strap points because the strap will not keep an adequate hold on the tank when the boat starts to get thrown around.
7) My own opinion again, but having had the boat out in a 6 foot swell with a fairly short distance between crests and a good wind blowing, I grew a bit alarmed at the way the boat creased up at the point where the tubes start to point towards the prow. Normally it feels fairly solid, but watching the whole front of the boat bend up including the floor, and the tubes crease up I decided it was time to turn around....also bloody wet and uncomfortable
It was RIB weather not SIB weather. I guess what I am saying is keep an eye on the conditions and be aware of the boats limitations.
Hope this helps - PM me if you have anymore questions.