PIREP - Reiff Preheat Systems

Quoting from the installation instructions:
"Installation of this heater is a minor alteration and does not require a
Form 337 or STC , in accordace with FAR Part 43 Appendix B. It does not
require an A&P to install it, but the installation should be inspected and
signed off by an A&P..."

Partner and I interpreted this to mean an A&P signoff was NOT
required, just recommended. Is my Reiff sump heater installation
illegal without the A&P signoff?

why does someone **** away $150+ on a heater which doesn't require
a 337 or an STC when you can get the same thing for $35.

Is there something legal and similar that costs $35? Or are you
referring to fabricating a heater using A/C duct and a blower? $35
won't buy you much in terms of a space heater.

I can't see how that would be as efficient in warming the oil as
putting 125 deg heating strips directly on the oil sump?

Greg