First, thanks for all the replies so far.
Reggie, I didn't know the Fram HPG1 was the standard Glasair filter, this kind of information is hard to find. Glad to know you are having success with it. Is the HPG1 used in the Glasair completely standard, or does it have a quick drain added to the canister? Do you use the standard HPGC1 filter element?
Walt, I always appreciate your knowledgeable comments and believe me, no offence taken. I'm an engineer and am used to reading component specifications and then trying to meet them in systems that I design, which is why I take Precision's recommendations seriously. Having said that I found that Diamond uses a single Andair GAS375 (70 micron) in their fuel system for the DA40 with fuel injection, so it is clear that Precision's recommendations are just that. What I would really like to find is a tee type filter with exactly a 32 micron rating, with a cleanable stainless steel mesh filter, with a clogged filter bypass valve and a port for a clogged filter indicator. A filter with these features is fairly common for hydraulic systems, but none of them that I researched were light enough and small enough for my fuel system. I do take the advice about cellulose based filter elements being susceptible to water contamination/clogging seriously. I'm not looking for someone on this site to "bless" a particular solution, but trying to make use of the expertise available to make a better decision. So this thread is still part of my research, and yes, I will consult the sources you suggest.
Stan, yes it is easy to drill the connector bolt between the head and the canister so it can be safety wired. I would prefer a choice of filter elements in the HPG1 so I could choose the 32 micron recommendation, but there is only one filter available with this assembly.
What I am trying to achieve with my fuel system is to have sufficient filtration upstream of the boost pump to protect it from particulate contamination (Andair GAS375 in each wingroot), and sufficient filtration downstream of the boost pump to protect the engine driven pump and injection system from particulate contamination, including contamination from a worn boost pump. I also realize the need to protect against water contamination, which so far includes drain valves in each tank and in each wingroot gascolator.
I do realize that the filtration and coalescing elements in the FBO fuel systems make both types of fuel contamination very unlikely, but I still prefer to design a system to account for unlikely conditions.
I've recently found a fuel filter used on Piper Senecas and Navajos which may be suitable. This is a tee type filter with a removable canister which houses 5 cleanable filter elements. It also appears to have a clogged filter bypass valve. However, both the Senaca and Navaho have the filter located upstream of the boost pump. Does anyone know the filtration rating and pressure rating of this filter?