Listen to UMD..

I have a Roubaix and a Tarmac.

I found the fit of the Tarmac a tad aggressive compared to the Roubaix. I had my Tarmac set up with a 6d stem flipped up and 15mm of spacers above the cone.

As this season has worn on and my riding has gotten more race oriented, and my strength and flexibility has improved, I have slowly lower the stem by moving spacers above the stem.

Yesterday I finally flipped the stem down and placed the 15mm of spacers back below the stem and have a fairly agressive drop. I did have to replace my 110 stem with a 100 to keep my reach the same.

I still ride the Roubaix, but only when doing easy rides or ones with lots and lots of climbing (it's a compact)....

I know I'm rambling here, but give it time...You will see as you ride more you will be able to handle that aggressive fit a bit better.

And as UMD says...The 54 will probably make things worse since it has a lower head tube. You would also being showing a ton of seat post.