after a few attempts... I was like "meh"
You have just described the entire span of time of my owning Saint Dragon before selling it!
Twin Cobra. I swear I was doing extremely well until stage 5. I had like 12 extra lives, all gone lol.
Kyuukyoku Tiger is really, really easy on the PCE up until the halfway point, which is where it starts showing some backbone.
Along with its slow start, its biggest flaw is that when you finally do loop it after 10 stages, the difficulty resets! After nail-biting aggression and dodging you are swung back to easy-peasy by comparison. After this, I gave up from boredom and intentionally suicided by 2-3. The Genesis port is hard right from the get-go, but
maybe for the wrong reasons (huge sprites + zoomed-in screen means you are always in danger). It has its fans.
Still, those final 5 stages are something else - very wicked and tricky to maneuver. Good luck getting past that hump. Remember: blue weapon only! Learn to love the bomb! Be attitude for gains!