I'd vote for a full professional Retul fit. I'm pretty cheap and very mechanical, and I can read and watch DIY videos like anyone else. I dialed in my new carbon bike last may. I'd go about 40 mi ok but then I'd get sore lower back and numb hands and arms, etc. The hotdogs in my bike club all kept telling me "got get a fit from John at Racer's Edge."

Finally I made the appointment. Long story short - It was the best $150 I've spent on my bike. Period. Replaced the stem (shorter) and seat post, (set back). John said "man, your bike is really pretty close. I don't often see them so close." Now, I never said that I had tried to dial it in, so I know he wasn't blowing smoke.

The real point is that "Close" may count in horseshoes and hand grenades, but not so in road bikes.

Note also I believe you said you other bike is lugged steel. Nothing short of a lazy boy will be as comfortable. IMHO.