tacoben, first thing to consider is what draw weight you are planning on shooting with the compound. That will determine whether the 3-28's will work out of the compound and what length and point weight to use in them. Do not base your arrow building on the min arrow weight. That is only a reference and assumes you are shooting the maximum draw weight on the bow. Plus it is an outdated min to boot. Just make sure you keep your total arrow weight such that the total arrow weight divided by the draw weight of the bow is greater than 5 (>5gr/#). This is considered an industry "norm" for the min arrow weight.
Second, as was mentioned before, drag is important. The heavier vane may cause your downrange velocity to drop off more quickly than a smaller vane. Hence making it more difficult to reach 90m. Especially on a Mach-9 with its mild cams.
Even more important on the vanes, however, is the affect of wind in terms of drift. Bigger vanes will drift more, I believe, than a smaller vane. Most compound target shooters use 1.5" to 1.87" vanes for 90m in comparison. If very careful, I imagine you could cut the vanes down to size. Many 1.5" and 1.75" vanes have the same height profiles as the larger sizes offered by the same manufacturer. Just need to be sure every one is cut exactly the same.
If you give us some idea of your draw weight and draw length on the 9, I'm sure someone would be able to give you some idea if the 3-28's would work out for you. I'm guessing, for example, that if you are shooting a 29" arrow (can usually run the arrow shorter than the AMO draw length of the bow) in the low-50# range on the 9 that a 3-28 w/ 100gr points would be right in the neighborhood of an acceptable arrow spine. Maybe a little stiff for the recurve, but possibly close enough that you could at least play around with the tension on the plunger to get them to work out of the 'curve for playing around. May need to suck in the sight bar (move sight bar in to shortest setting) on both the compound and the recurve to get out to 90m.
Hope any of this helps.............
>>------->