First of all, what the hell are you doing at 30K? Last time i was up there was in an FSO, and the 152 worked excellent for me, i can tell you.
Then, well if you think the 152 is steady and handles well at low alts, youre either a masochist or know nothing about other aircrafts.
Finally, the spit14 handles very "stiff" at low altitudes, compared to other aircrafts. Its due its light airframe - very powerful engine - relatively high aspect ratio combination.
True, i have never been above 15k in a spit14.
Btw Hlbly's report is more than interesting. Physically thinking, those results would be next to inpossible (vs the spit9), but i can never know...