Is it possible to tape over some of the finger holes and convert the xaphoon into diatonic instrument, instead of a chromatic instrument with an insane fingering pattern for notes? 
The Xaphoon has, at the best of times, a fairly loose association with the Western musical scale as it is generally recognised.
Iâd have thought youâd do far better to just ignore the fingerings you really donât like and work on the assumption that those notes arenât in the instrument"s scale; I really canât imagine that taping some holes is going to make things any better âŚ
Looking at the fingering chart on the manufacturerâs web-site http://www.xaphoon.com/fingeringcharts.html it would seem a diatonic pattern is (almost) available in the key of C until you get up to B ⌠so not quite an octave, but may be worth considering if you already have an instrument. Personally Iâd block the unused holes with beeswax, no chance of a leak and looks neater (traditional, even!)
If youâre looking for something a little âdifferentâ and have yet to make a purchase Iâd suggest a âchalumeauâ, basically a keyless clarinet, available economically from Hanson http://www.hansonclarinets.com/Hanson_Clarinet_Company._Making_Music_in_Great_Britain./Chalumeau.html or in wood from several other manufacturers at varying prices. I have a Hohner âPocket Clarinetâ, much the same thing ⌠itâs a lot of fun 