In the previous paper the flat bottom effects on wave-making resistance was investigated with respect to the non-bulbous Pienoid models. This paper is an extension to the similar problems of designing the bulbous Pienoids with least wave resistance. The essential conclusion of the previous report is the fact that the observed free wave amplitude due to the additional bottom doublet is as small as nearly half of the corresponding linear theory. For the purpose of ascertaining the adaptability of this conclusion to the case of bulbous forms, three bulbous Pienoid models M 23, M 24 and M 25 are designed and tank-tested as follows : M 23 (α _B =0, where α _B denotes the reduction factor of the bottom doublet wave), i. e. the bottom doublet is completely neglected. M 24 (α _B =1), i. e. the bottom doublet wave is assumed as large as the linearized theory M 25 (α _B =0.4). Based on each assumption, the optimum combination of the side source and the bulb singularity is obtained at F_n =0.277 ( K ₀ L =13) for the described draught and displacement. In this procedure, so-called μ-correction (μ _S ) to the side source ought to be taken into account adequately. However, herein as the preliminary step, no correction was applied to the side source (μ _S =0), which resulted in some confusion as follows. Experimental results show that the first medel M 23 (α _B =0) is the best among the three tested models. However, this fact does not necessarily conclude that the first assumption α _B =0 is correct, because the present assumption μ _S =0 is not acceptable. To ascertain this, the fourth model MTM-4 is redesigned (but not tank-tested) by adopting the side source correction μ _S =0.4 as well as the bottom doublet correction μ _B =0.4. The obtained lines of MTM-4 is found as very much the same with those of M 23 (Fig. 13). This may suggest that the optimum bulbous Pienoid with a flat bottom can be designed by applying μ _S =0.4 and μ _B =0.4 with no correction for the bulb singularity.