Single-wall carbon nanotubes (SWCNTs) with open ends can be readily filled with a wide variety of organic molecules through simple liquid exposure. Ingestion of such molecules affects the extrinsic environment experienced by the SWCNT, and holds promise for controlled modulation of intrinsic SWCNT properties. To date optical linewidth narrowing, transition energy shifts and fluorescence enhancement as well as density modulation have been demonstrated. However, the dependencies of the properties on the filler molecule properties is observed to be non-uniform across filler and SWCNT (n,m) combinations. Of particular note is the combination of filler molecules and SWCNT structures of similar size, for which sieving and non-bulk arrangements of the filler molecules can be anticipated. Results in the small-diameter (n,m) SWCNT limit will be presented isolating the effects of filler insertion on the nanotube properties as a function of diameter, and implications for filling-based nanotube property manipulation.