<p>Tall thin-walled structures are often a key component in aerospace, automotive, and other applications. Additive manufacturing of such structures using fused filament fabrication (FFF) is particularly challenging when good mechanical properties and geometric accuracy are desired. This work aims to enhance the flexural strength of such structures without compromising their geometric accuracy. In this work, a previously demonstrated technique of improving layer-to-layer bonding by providing additional thermal energy during printing is utilized to print thin-walled structures that are much taller than standard tensile test specimens. Mechanical characterization of parts printed with polylactic acid (PLA) is carried out using a 3-point bend test. In addition, geometric deviation, surface roughness, and interlayer bonding potential are also evaluated. Results demonstrate that providing additional in situ thermal energy more than doubles the bending strength and significantly increases the bonding potential while maintaining or exceeding geometric accuracy and surface finish, compared to a standard specimen. Results indicate structural performance improvement for a tall structure with both single-bead and multi-bead walls. This work demonstrates the potential for printing effective tall thin-walled components using the in situ heating technique to meet practical strength requirements in a variety of applications.</p>