Substrate heating

I think I understand this pretty well now.  I can put together a DIY
instruction  pack for the list.  The problem is that it is not real cheap, even
DIY, but of course it is a LOT cheaper than Dupla.  The budget looks like: 
Thermostat $15 (or use scrap parts), transformer $15-50 (depending on wattage
desired, in some circumstances, transformer can be omitted), wiring $3,
transformer case $5, heating cable $1/foot, cable clips $2-4, sealant, tubing
$4.  Here is the question:  is this interesting enough for me to put in a bunch
of hours getting it together?  Please give me your answer PRIVATELY (off the
list), less junk traffic that way.   Thanks.   Dave

Dave Gomberg, Experimenta      San Francisco CA USA   gomberg at wcf_com