I took the liberty of adding the following lines to the weapons.ru file (In my case, weapons.properties):
#####################################################################
# A-26B
#####################################################################
A-26B.default Default
A-26B.4x1000lbs 4x1000 lb. Bombs
A-26B.6x500lbs 6x500 lb. Bombs
A-26B.16x100lbs 16x100 lb. Bombs
A-26B.2xMk13Torpedo 2x Type Mk13 Torpedo
A-26B.14xHVAR5 14x5"HVAR
A-26B.10xHVAR5+2x175Napalm 10x5"HVAR + 2x175 Napalm
A-26B.10xHVAR5+2x154DT 10x5"HVAR + 2x154DT
A-26B.4x1000lbs+10xHVAR5 4x1000 lb. Bombs + 10x5"HVAR
A-26B.6x500lbs+10xHVAR5 6x500 lb. Bombs + 10x5"HVAR
A-26B.6x500lbs+10xHVAR5+2x175Napalm 6x500 lb. Bombs + 10x5"HVAR + 2x175 Napalm
A-26B.16x100lbs+10xHVAR5 16x100 lb. Bombs +10x5"HVAR
A-26B.16x100lbs+10xHVAR5+2x175Napalm 16x100 lb. Bombs +10x5"HVAR + 2x175 Napalm
A-26B.4x500lbsExternal+10xHVAR5 4x500 lb. Bombs (External) + 10x5"HVAR
Sorry but this list is wrong ! Due to an error in the Java code!
If you do not see "none" to the end of the payloads is that there was a mistake ...

@mac1
In A_26B Class, please, change :
"BombGun250
bs" ===> "BombGun250
lbs"
change
s = "2xMk13";
a_lweaponslot = GenerateDefaultConfig(int1);
a_lweaponslot[19] = new Aircraft._WeaponSlot(3, "BombGunTorpMk13", 1);
a_lweaponslot[24] = new Aircraft._WeaponSlot(3, "BombGunTorpMk13", 1);
by
s = "2xMk13";
a_lweaponslot = GenerateDefaultConfig(int1);
a_lweaponslot[19] = new Aircraft._WeaponSlot(3, "BombGunTorpMk13", 1);
a_lweaponslot[20] = new Aircraft._WeaponSlot(3, "BombGunNull", 1);
a_lweaponslot[24] = new Aircraft._WeaponSlot(3, "BombGunTorpMk13", 1);
a_lweaponslot[25] = new Aircraft._WeaponSlot(3, "BombGunNull", 1);
Here is the list (for future version 409)!#####################################################################
# A-26B
#####################################################################
A-26B.default Default
A-26B.6x500lbs 6x 500lbs Bombs
A-26B.16x100lbs 16x 100lbs Bombs
A-26B.2xMk13 2x Mk13 Torpedos
A-26B.14xHVAR5 14x HVAR 5" Rockets
A-26B.10xHVAR5+2x175Napalm 10x HVAR 5" + 2x 175gal. Napalm
A-26B.10xHVAR5+2x154DT 10x HVAR 5" + 2x 154gal.
A-26B.4x1000lbs+10xHVAR5 10x HVAR 5" + 4x 1000lbs Bombs
A-26B.6x500lbs+10xHVAR5 10x HVAR 5" + 6x 500lbs
A-26B.6x500lbs+10xHVAR5+2x175Napalm 10x HVAR 5" + 6x 500lbs + 2x 175gal. Napalm
A-26B.16x100lbs+10xHVAR5 10x HVAR 5" + 16x 100lbs Bombs
A-26B.16x100lbs+10xHVAR5+2x175Napalm 10x HVAR 5" + 16x 100lbs + 2x 175gal. Napalm
A-26B.4x500lbsExternal+10xHVAR5 10x HVAR 5" + 4x 500lbs Bombs (External)
A-26B.4x250lbsExternal+10xHVAR5 10x HVAR 5" + 4x 250lbs Bombs (External)
A-26B.4x100lbsExternal+10xHVAR5 10x HVAR 5" + 4x 100lbs Bombs (External)
A-26B.6x500lbs+4x500lbsExternal 6x 500lbs + 4x 500lbs Bombs (External)
A-26B.6x500lbs+4x500lbsExt+2x154DT 6x 500lbs + 4x 500lbs Bombs (Ext) + 2x 154gal.
A-26B.6x500lbs+4x500lbsExt+2x175Napalm 6x 500lbs + 4x 500lbs Bombs (Ext) + 2x 175gal. Napalm
A-26B.2x154DT+4x1000lbs 4x 1000lbs Bombs + 2x 154gal.
A-26B.PTO_Default Default (PTO)
A-26B.PTO_8xHVAR5 8x HVAR 5" Rockets (PTO)
A-26B.PTO_2x154DT+8xHVAR5 8x HVAR 5" + 2x 154gal. (PTO)
A-26B.PTO_4x1000lbs 4x 1000lbs Bombs (PTO)
A-26B.PTO_6x500lbs 6x 500lbs Bombs (PTO)
A-26B.PTO_16x100lbs 16x 100lbs Bombs (PTO)
A-26B.none Empty