You will never have interference WITH the ignition. You can have interference BECAUSE of the ignition. Some ignitions are better than others in that respect. I don't know what the CRRC has.

Heat is a very great enemy of ignition systems, regardless of maker, but again some ignitions are much more tolerant of heat than others. Consider how much heat will be radiated by the muffler that will impact the ignition. the back of an engine normally, and I repeat normally, does not generate a tremendous amount of heat. The jighest generators of heat are the cylinder head and the muffler.

Will the heat radiated by the head and muffler become trapped inside a cowl? If so, reconsider the location of the ignition. Inside the firewall would probably be better since that area generally does not receive or trap much heat from the engine compartment.