yeah i agree with a good tune it is possible and low timing, that dp turbo is a good turbo as well, the t25's and 28's just create alot of backpressure at higher boost levels than the dp turbo. Thats why you could easily get away with 16psi or so on a t3t04 60 trim on 10:1's with a good tune, low low backpressure will help keep heat out of the cylinders when it shouldnt be there.
I dont think coating your pistons will help that much either if your just running too much boost. Its true on the a/f ratio as well. My a/f was around 11.8-12.0:1 when i was running my setup. My base timing was at 15 as well. This was on all my motors but mostly 9.5:1's
I was told later i should have been around 13 deg base timing and around 11.0-2:1 or so to help keep temps down but then again you can run a lower boost level with more aggressive timing and a/f ratio and make just as much power or pretty close and probably have a better spool time.
This is why my setup on my t28 was sooooo much faster than my t25 setup with 17psi spike holding 12-13psi. It stomped it all over the powerband. I was not only just slightly breaking the tires loose in 3rd from 50 roll but spinning them till about 80-85mph, Plus even on the t25 setup it seemed as though with the boost at 10psi seemed faster than at that 17psi spike other than the fact that the spike would build insane torque down low which would break the tires loose in third, at 10psi i could not do that.
Its all about turbo sizing, a/f, boost level, and timing. So keep everything in check with the right settings and you should have a responsive setup.
Id say on a 10:1 motor with 8-10psi of boost, 11.8-12.0:1 a/f ratio will be a safe, reliable, very responsive setup. if you wanna go higher, drop your timing down 2 deg or so and drop the a/f to 11.0-11.2:1 to help keep temps down.
On a t28 its higher, and on a bigger turbo than that its higher again.