[ver 0.1.16]

The slot feels wasted on explosives and oil barrels. Use signal R to control explosion radius

To implement, edit control.lua:

line 107: this code does not work, replace with
local connector
for _, glob_silo in ipairs(storage.missileSilos) do
if glob_silo.silo == silo then
connector = glob_silo.connector
end
end

line 166: move to the start of function def
line 170-174: remove, no longer needed
line 188-189: remove, no longer needed
line 165, 181: unused local variable, could remove

add after line 145:
if connector and connector.valid then
radius = connector.get_signal({ type = "virtual", name = "signal-R" },
defines.wire_connector_id.circuit_green) or 0
if target_x == 0 then
radius = connector.get_signal({ type = "virtual", name = "signal-R" },
defines.wire_connector_id.circuit_red)
end
end

Sorry but I won't change the spread mechanics. The missile-silo can be operated completely without the circuit network and I want to keep it that way.
By the way, the code lacks a way to cap the spread. High R settings could lead to problems. If you want to keep the edited version for personal use I would add that.