I still believe a high Spd3 acceleration will be desired on the times you're navigating the track rather than side attack cancels on the rail. I've taken a quick look at the rails, and they seem to make you lose speed pretty badly.
Optimal pattern of a right-side rail cancel is one or two frames off the rail, and one frame on the rail. So at best, you're spending two frames with "normal" acceleration (-16 due to Side Attack) and one frame where you're slowed by being on the rail. If you have boost going, you'd power through the mess without issue (as seen in my quick TAS). Without boosts, your speed will decline rather readily.
I keep wanting to push the virtues of reading hexadecimal. It will give a nice, clear, thousands-place boundary on the horizontal or vertical parts of the tracks. I know I most definitely wanted the hexadecimal display in my quick TAS, but that's me.
It's also not exactly trivial to know how to tweak your momentum just right. Starting the chain properly is probably the difficult part, as you're not in the ideal position to start with. Continuing it with the boosts I had wasn't too hard, I just had to figure out how to change my facing to tweak the position perfectly. Without boosts, you're going to be constantly losing speed keeping up with the side attacks, and I don't know how much it is worth.
On a side note, taking the best possible LR drift (464) on the best possible speed (yellow arrow, under 2560), and doing this while driving at 90 degrees, your true speed is around 3000, or 1500 km/h. My earlier calculation with boosted Dragon Bird on rails is around 1530 km/h, so these side attacks definitely work somewhere. The gain is attractive, I'll say that much, but I never did take a look at it without boosts.
The average of the first three frames of the side attack is 1904. Boost-free, you're going to trash your speed quickly, so give yourself 1200 internal speed for the average, and since you more or less have to drive straight, we've got the worst angle we can use, so we end up averaging 2250.
Crazy Bear has some crazy drifts it can do, so let's take the 1944 top speed and apply the 464 LR drift at 45 degrees. The average here is 2295. Note that Crazy Bear doesn't have to recover speed afterward since we're just doing a normal LR drift, rather than rail-canceled side attacks which drops your speed.
Starting to look like these side attacks should be used sparingly on the first lap and also sparingly whenever you couldn't fit in more boosts in later laps. Based on these numbers I'm analyzing, it does seem like you'd want to only use them when the alternative is hitting max speed and no longer accelerating. An 8 for 4th gear acceleration would let you take the side attack loss a lot more easily.
At least Maximum Velocity doesn't have side attacks, so you can avoid optimizing this problem over there.
