Comparison between observations and our model results of thick-to-thin disk scale length ratios, r_{d,   thick}/r_{d,   thin}, as function of circular velocity, v_cir, from our minor merger models with two gas fractions, f_gas = 0.1 and 0.2, and two clumpy gas-rich disk models (gSb+u1 and gSb+u2, see Sect. 2 for the notations). Observations are shown for samples of late-type spirals (Yoachim & Dalcanton 2006, solid black and open circles), (Wu et al. 2002; Abe et al. 1999; Neeser et al. 2002, diamond and triangles), a sample of early type galaxies (Pohlen et al. 2004, diamond with a cross) and the Milky Way (Larsen & Humphreys 2003, square). In addition, a cosmological simulation is shown (from Brook et al. 2004, asterisk).