Hmmmm....not my area of expertise, but the front of the pilot does not seem to be the optimal location. Seems more likely that something could bang into it in a smash. Ideally, you'd get as far away from the engine, fuel tank, etc. as possible, so in the utter worst case, the wisk-broom and garden hose detail knows where to show up.
Yet you've got a portable device....not a permanent install like an ELT.
What seems to see the least damage in accidents? The tail and the wingtips. Perhaps a recessed pouch forward of the horizontal stab or on a lower wingtip. Use velcro inside the recess to hold the PLB, and put a fiberglass cover over it (hinge the front edge, use Velcro to keep it shut). Pop it in when you get to the airport, pull it out when you go home.
A less complex location, probably 95% as safe, would be on the BACK of the pilot's seat. That way any crash forces, etc. would need to get through YOU before the broom and hose folks show up, and you're not likely to care. A lot of the Nieuport seats I've seen don't go the whole width of the fuselage, you could slip the unit around to a carrier on the back of the seat.
Then again, if you've got it in the mode where it's dropping breadcrumbs, it might not make a whole lot of difference. A Nieuport isn't going to get that far in five minutes. The way I fly, the DEBRIS field would probably still overlap the breadcrumb location. :-)
Edit: My inexperience with PLBs is showing...I forgot they typically include a "Mayday" button, and thus should be close enough so that a damaged pilot can activate it. Not only should it be protected as well as possible, it should be positioned so that the pilot can activate it with either hand. Shoulder harness wouldn't be bad...but depending how big it is, you might consider hanging it around your neck on a badge lanyard, tucking the unit into a shirt pocket. The lanyard would make it easier to find if you're damaged or in shock.
Ron Wanttaja