I'd suggest to create a couple of planes with the desired loadouts, and then use a text editor to find those planes and, hence, their loadouts/pylons within the mission file. An example for your request could be (rockets on pylons):
["payload"] =
{
["pylons"] =
{
[3] =
{
["CLSID"] = "{FW_190_R4M_RGHT_WING}",
}, -- end of [3]
[2] =
{
["CLSID"] = "{FW_190_R4M_LEFT_WING}",
}, -- end of [2]
}, -- end of ["pylons"]
["fuel"] = 388,
["flare"] = 0,
["chaff"] = 0,
["gun"] = 100,
}, -- end of ["payload"]