Palmer is a brave man to be the first to answer this request. My hat is off to him, as he obviously is commenting on what he clearly has experience.
My first comments are hopefully obvious; something which is often
lacking in the field of engine-building. For the production of maximum engine power in a modern four-stroke engine the MAIN parameter to this end is
Compression Ratio.
To simply install hi-comp pistons in any Ducati engine, with no further checks, and to expect a power increase, is pure folly. Indeed, it is quite likely that just "dropping" different pistons into your engine may simply prevent the engine from turning!
As Palmer states, you need to check (quite) a few things:
Is your cylinder height standard, or has a previous owner machined some metal from the cylinder base (to increase CR) and are you running with or without cylinder base gaskets?
Are you using "lumpy" cams? Using racing cams like NCR 7's can easily lead to piston-valve contact for the uninitiated. The same applies to
larger-than-standard valves.
Its also best to check your engine one cylinder at a time. First, just fit one piston, install the head, including belt, and turning the engine by hand, ensure that your engine actually TURNS! This may sound a trifle comical to the casual onlooker, but MY experience with
tuned-to-middle-C Pantah engines says that piston/valve/squishband contact is often the norm, rather than the exception!
Anyway, once these basic checks have been done, its time to steal your kids' plasticene, and get down to actually MEASURE the squish-band clearance,and piston-to-valve clearances.
Palmer's values for the various clearances are excellent guidelines, although I must admit that MY racing Panath engine enjoyed considerable
smaller squish clearances, usually 22 to 27 thou.............!!!