You may get away with the longer exhaust timing but you'll lose low down power for acceleration. IMO the crank closing timing is far too radical though and I'd tend to leave it as it is because it's got quite a good closing as is. Engines only work with high exhaust timing if they use a proper tuned pipe and from what I've seen a car exhaust system is far from being tuned. They're more like a muffler with maybe a slight bit of resonance at some point.

Here's an example of the timing for an engine that's designed for one purpose and one purpose only. Flat out running developing the maximum possible power with a full length tuned pipe. This is an OS 40PS Pylon racing engine.
Transfer opens 64 BBDC
Boost opens 63 BBDC
Exhaust opens 91 BBDC
Inlet opens 38 ABDC
Inlet closes 64 ATDC

But powerwise what's it like? Well with an open exhaust (no muffler, no pipe) it's totally gutless. Peak HP is 1.4 @ 20,000 with a nice smooth HP curve. But put a full length tuned pipe on to take advantage of that high exhaust and things get a bit different. Basically it can't run between 16,000 and 23,000 revs...it's either one or the other. Meaning it's either off the pipe or on the pipe. At 16K it's developing just under .8HP but at 23K it's developing 2.6HP and doesn't reach a peak until 26,000 where it's putting out 3.14HP. A car engine set up like this would be completely undriveable. Slow to accelerate out of a corner (gutless) then suddenly having 3 times the power with no control in between.

What this is all supposed to show is that there's a point of overkill when changing timings. You can make a gain in one area but have terrible losses in other areas. If model cars had oval track racing then you could get away with wild timings and a proper pipe but not on twisty tracks.

On the point of rod/stroke ratios as grits said, the higher the ratio the better. This OS has a ratio of 1.94 which is excellent but it's something that can't really be changed on our engines.