  Long and thin scanning force cantilevers are sensitive to small forces, but
also vulnerable to detrimental non-contact interactions. Here we present an
experiment with a cantilever whose spring constant and static deflection are
dominated by the interaction between the tip and the surface, a regime that we
refer to as ``overcoupled''. The interactions are an obstacle for
ultrasensitive measurements like nanoscale magnetic resonance imaging
(nanoMRI). We discuss several strategies to overcome the challenges presented
by the overcoupling, and demonstrate proton nanoMRI measurements of individual
influenza virus particles.
