Quantitative relaxometry in the brain is appealing because of its microstructural sensitivity. Estimating bulk parameters assumes a single relaxation time per voxel, which is only valid when the residency time is short with respect to T1. In reality, the relative contribution of sub-compartments will depend on flip angle and echo time. Here, we simulate a two-compartment model (myelin and intra-extracellular water) and estimate T1 with FA-specific signals derived via three estimation schemes. We quantify the impact of myelin water fraction, residency time and transmit field inhomogeneity on these estimates and find good correspondence with in vivo T1 estimates at 7T.