I've pre-shaded and painted the undersides now.
The P-40E-1, painted SMS RAAF Sky Blue;

The P-40E, painted DuPont 71-021 Sky Type S Grey, for which I used Tamiya XF-14 J.A.Grey;

The Tomahawk II, painted SMS Azure Blue;

All undersides look great, my friend @michaelt!

P-40E upper surfaces painted.
I painted and masked the upper insignia blue before painting the camouflage.
The decals come with a pair of Blue/White upper roundels with separate red centres to cover the white for the scheme that has the older RAF style Blue/Red roundel.. I want to use the later Blue/White roundel on another build (one day) so I will just use the Red centre decal on this build.
The RAAF overpainted the yellow surround to the fuselage roundel, so I sprayed Foliage Green and masked before painting the camouflage there and will add the Blue/White/Red roundel decal later.

The colours are my interpretation of Dupont equivalent colours;
Dupont Dark Earth - Gunze H37 Wood Brown
Dupont Dark Green - Gunze H78 Olive Drab (2)
and
RAAF Foliage Green - SMS PL78 Foliage Green

2 attached images. Click to enlarge.

Excellent paintwork, Michael @michaelt

Decals are on the P-40E.
The fuselage roundels provided by Ronin Decals are too large so I used a pair of 25" (13mm in 1/48) Type A roundels from the Eduard Spitfire Mk.I Dual Combo.
Unfortunately, I miss calculated the diameter of the fuselage masks to convert the Type A1 (Red/White/Blue/Yellow) roundel to a Type A (Red/White/Blue) roundel - they should have been 35" (18.5 mm in 1/48) but I cut the masks to 42" (22.2mm in 1/48) which would be right for a 30" Type A roundel.
At least I can get that right for the P-40E-1.

Tomahawk IIB:
Upper surface colours are:
Dark Earth - Tamiya XF-52
Mid Stone - SMS PL75 Mid Stone

Both look great, Michael @michaelt. I wouldn't sweat the size issue with the roundels too much. I don't think any one will notice.

Really nice work all around, @michaelt.

Looking great, Michael @michaelt
A bit bright indeed, but they might turn slightly darker after applying a coat.