I fully agree with the comments of the others. Especially Robi's advice is good when considering your crew make-up.
It is my opinion that if you two are currently sailing the H20 then the F16 will be a noticeable improvement. Yes you are a light crew, but the H20 should be noticeable less suited to that then the F16.
One trick is to order the boat with a mainsail cut for your combined crew weight (or just a little above it). This can not be done with the H20. The result will be more controllable boat and one that is easy to depower for you. It all dependent on sailing skill but with sufficient amounts of it available I really don't see why you'll need to back off were you would be comfortable with either the H17 ot H20. Several of us singlehand the F16 to in the 20 knot wing range. And that includes setting the spinnaker. Just adjust the boat to suit your weight and body make-up, something that is fully possible under the Formula rule set. There are no class rules preventing such modifications, so make full use of them. Actually one result of this is that both light and heavy crews are more comparable in performance with these mods. Heavy crews can use them to power the boat up a little more and ligther crews can use them to depower it some more.
The F16 will be easily righted by your 255 lbs with only a righting rope. I weight 195 lbs (=88 kg)and I right it singlehandedly unaided in even the most difficult conditions (flat water, no wind). Additionally no weight needs to be carried by you.
The F16 will totally replace the H17 and H20. It will be an improvement over both in several aspects. Moving it about on the beach and putting it on the trailer will be one. Stepping the mast another. If one suddenly decided to stay on the beach then that is okay as there will be no need to rig (or bring) the other boat.
It will certainly be cheaper then maintaining two seperate boats.
Any other information or suggestions are welcome.
If you are contacting Jill Nickerson about the Taipan design then ask her about the Viper F16. This Viper F16 is the official replacement of the Taipan design by the builder AHPC. See my other posting for more info. It will be significantly cheaper then a new Taipan and will feature all kinds of things not found standard on the Taipan. It is expected to be better suited to F16 sailing then the Taipan. Having said this, as a second hand option the Taipan should still be high on your list.
In the way of second hand options there are Taipans, Stealth and a (demo) Blade on offer. Especially the second hand Stealth is attractively priced right now. Ask Eric Poulsen for more info if interested.
But as my last comment is reserved for the best advice I have. Test sail the boats yourself and ask the owner to show you the different controls and have him show their effect. Flip the boat intentionally and right it yourself. Only then will you know exactly what can be expected and whether you are willing to invest in it.
Best of luck !
Wouter