Umm, not sure I buy this. Per article above (see Google dashboard image), over 55% of Android devices currently use Android 2.3 (Gingerbread) and about 13% use Android 2.2 (Froyo). Your testing plan leaves behind 68% of the Android userbase -- which is kinda huge.
FYI, when I build apps for my clients I tend to support Android 2.2 and above.
>> Use the application manifest's compatibility features to prevent the Play store from showing your app to users running with unsupported devices
There can be unintended consequences to this -- such as for example greatly impairing your marketing message.
Nowhere is that clearer than at a launch event. Say your app is ready to launch and you want to hold an onsite launch event. Based on your Play store exclusions, 68% of the people in the audience will have an unsupported device. Now for the fun part: on an unsupported device, your app simply does not appear in the Play store listings! Zero, zilch, nada, no results -- it's like your app does not even exist to those users. You now have a frustrated event audience, with all enthusiasm drowned out by the cries of people asking you why they can't find your app in the store. Not good.