of HI surveys, the measurement of HI masses continues to lag behind optical surveys. For example, in contrast to the $\sim$ 5000 detections available for the 40 per cent ALFALFA data release (Haynes et al. 2011), the main galaxy sample of the Sloan Digital Sky Survey (SDSS) contains more than two orders of magnitude more galaxies out to $z \sim 0.2$ (e.g. Strauss et al. 2002). For this reason, there is a long history of efforts that attempt to infer  from more readily available optical properties (Roberts 1969; Bothun 1984; Roberts & Haynes 1994). In the last decade, such efforts have been able to capitalize on large, homogeneous datasets, often in combination with multi-wavelength data in the UV and IR regimes (Kannappan 2004; Zhang et al. 2009; Catinella et al 2010, 2012; Toribio et al. 2011; Wang et al. 2011; Li et al. 2012; Denes, Kilborn, & Koribalski 2014; Eckert et al. 2015). These works have used different linear combinations of physical parameters to reduce scatter between the estimated and observed HI gas mass fraction (defined as  throughout this paper). However, despite the availability of extensive physical parameters, and the identification of the ‘best’ parameters for  estimation, the improvement in 