I wanted to resurrect this to mention that I did some research looking at the game memory and found where the game score is located. It's stored in a very strange way (see below), but the upshot is I figured out that extra lives are given every time you cross 50k with the ten thousands digit. In other words at 50k, 150k, 250k etc.

With that knowledge I did a heavily save stated run to kill as much as possible, noting the point values for various enemies along the way and found that it's just possible to get to 150k if you kill nearly everything in the game. I developed a route to do that and that's how I ended up with the 23:11, getting the 2nd extra life at the final boss allowing the crash on the final landing. I don't think 250k is possible unless there's some big score bonuses I missed.

For those interested, the score is stored in 3 DWORDs (8 bit values) at RAM addresses 0x7E4 (Tens/Hundreds digits), 0x7E5 (Thousands/Ten-Thousands digits) & 0x7E6 (Hundred Thousands/Million digits). Notice there's no Ones digit, that is assumed to always be zero and is tacked on when displaying on the score screen.

The other funny/strange part is each part of the score is stored in hex but treated as decimal when displaying. So a memory value of 0x50 at 0x7E4 which would translate to 80 decimal, shows up on the score screen as 50. I found this by accident when changing the score values and ended up with a score of "AA0" :P

As an example for a score of 1,256,340 the memory layout would look like:

| 34 | 56 | 12 |

| 0x7E4 | 0x7E5 | 0x7E6 |