Grayzee, I'm no fluids expert, but I can tell you that sounds terrible - it sounds just like what I warned against as the basic type of stuff to avoid.
Having two silicone transitions (they're just steps, really) from 2.5 to 2.75 and 2.75 to 3.0 does not make a gradual transition. Silicone parts are not the best place to do turns or reductions because they are usually very abrupt. When I referred to "long and smooth transitions," I meant doing something like cutting a 12" long, 3" diameter pipe lengthwise (removing a very narrow triangle) and welding it back so that one side remains 3" and the other is now 2.5", for example.
Doing it this way costs very little (less than silicone 90° transitions), looks groovy, reduces complexity, and causes far less disturbance than standard step transitions. A lot of guys think they're saving themselves money by avoiding a welder and, instead, having 10 silicone connections with 20 worm gear clamps - yuck!
I'm betting there's a thread around here somewhere with the likes of John Coffey and similar guys with clout and experience explaining this.