Not sure I would risk bleaching that Tigers Pennant. It's just not that bad, and the orange paint could conceivably bleed. Maybe Rob/Rob knows better, but I would err on the side of safety.
As for the Yankees... you'd need to carefully remove and re-apply the photo after bleaching. That one might be worth a try, as it's looking pretty rough, and is perhaps worth the risk. Perhaps Rob/Rob can chime in about the potential of red paint bleeding on that one.
I am not really a fan of the alterations being discussed. I have done it on rare occasion, and always disclose exactly what was done (if selling). But even then, who's to know what gets disclosed after the pennant changes hands a few more times? Therein lies the problem...
Trimming of the tip to form a point is probably the most prevalent alteration with vintage pennants, and is usually quite easy to detect if you know what to look for.
Cleaning a pennant is fine. Cannot even count how many times I've used scotch tape to lift off excess dust, debris, and especially pet hair. I think 75% of the pennants I've recently acquired have cat or dog hair inter-woven into the felt. If you have no propensity towards OCD, then nevermind and carry on.
