1200rallycar is right, I could (and have on occassions) taken my car to 8000rpm. There is no real power up there, but it will eventually get there if it has too - like when you get jammed in 3rd. Just out of interest, the A15 has a much longer stroke than my L18, and the same length rod as I use.

tertonga, any details on the piston and rod combo in that 9500rpm A15?

This is what I have learnt from various books and talking to engine builders. Any time you increase an engine's displacement you decrease it's responsiveness to cam timing. The biggest desensitiser is increasing stroke, because it reduces the rod to stroke ratio which determines some engine dynamics which are very significant in the 4 stroke cycle.

Increasing stroke (and decreasing rod to stroke ratio) will:
*increase rod angularity. This has a few impacts but I can only think of 2 at the moment; 1) decreases mechanical efficiency through increased friction; 2) reduces safe operating speeds due to increased stress to rod beams and piston skirts
*increase piston speeds across top and bottom centres. As these are where all the crucial valve events happen, the increased speed decreases the engines sensitivity to effective valve timing. This means the A15 will not respond as well as the A14 to the big maximum effort cams you need to get good power out of these little motors. This is a good thing for a street motor, as it is more forgiving to cam timing errors and where your cam gear limits the adjustability, but bad news for chasing peak bhp in a race engine.

The rule of thumb is that higher rod to stroke ratios are good if you are intending to run at sustained high rpm. Lower rod to stroke ratios work best at lower rpm and will tend to produce a broader operating range. best suited to road or rally applications. It's not always that simple, but a generally accepted guide.