Ideally I would like to use:

- sanwa 451 receiver
36.5 x 24.0 x 15.0mm

just to do the comparison the ko407s is 28 x 18.3 x 18.5 mm...

- s9650 servo

Length:1.42 in (36.1 mm)
Width:0.59 in (15.0 mm)
Height:1.14 in (29.0 mm)

- HW 1S ESC
43mm(L) * 36mm(W) * 33mm(H, with cooling fan)

The HW isn't small..

Maybe I should have bought a 12R5.2