Hiya Marzbarz.
Okay, first of all I'll admit I'm way more the 'lee in any tickle relationship i've ever had. And that's the way I like it.
BUTTT, I also can enjoy the turn about tickles just for variety and let's face it, don't we all love to touch our guys in a way that brings out a cute reaction.
😛
Anyway, Marz, being barely 150cm tall and 46 kg soaking wet, I can so relate to your plight of ever making a successful tickle attack.
but I have devised a couple of devious strategies.
First of all, the old massage trick can work if I manage to do it on the bed sitting on his back. But even then it's critical to sit above his waist so my knees prevent him from bringing his arms flush to his sides. That way I can go to town on his ribs.

I just have to watch out for the occasional desperate reach-back grab for my feet. That's where being on a bed can help. I can use the folded blankets for protective padding.
Another option is to be strategically close by when he is taking his shirt off. At just the point when he pulls the back over his head, he's particularly vulnerable. with the shirt blocking his sight and twisting up his arms it's just a matter of keeping the initiative tickling him so he can't coordinate his moves enough to get the shirt off.
Lastly, the most tried and true way to tickle him into a girlish whine is with the help of friends. His or mine. I don't know about the guys on this forum but I've never had much difficulty getting a guy's friends to help hold him while I proceed to tickle him into quivering giggles.
😀 - of course I have to admit they usually end up tickling me insane afterward. Which you may not be wanting.
So there is always your own friends or his female relatives.
I hope these help a little. And I hope to hear of the moment when you get him good.
😛
Here's cheering you on, girl!!
Many blessings,
chickles