Drop to 14lb during 2-handed transition?

I've recently switched to two handed - just a couple weeks now, and bowling is fun again as I don't have to deal with my thumb issues, it's been great other than the usual beginner stuff, form sucks, coming way around the ball, etc.

I use 15lb balls. I've bowled league twice now two handed and usually play three or four games after league. Due to these new changes, my back and throwing arm bicep are sore the next day.

Would it be beneficial to grab a 14lb ball to learn the two handed technique? Would it be beneficial to just drop down completely to 14lb for bowling two handed? I know my speed will come back eventually with 15lb - right now I've lost 2-2.5ish mph vs my one hand throw.

Just wondering if anyone has gone from 15lb to 14lb and is happy with it? I'm not a youngster (early 40's) so just wondering what the move is here. I have the revs with the 2H so I'm thinking maybe dropping down in weight will get my speed up as well and if there are any downsides to going down to 14.