Question re: repair fitting

Good morning folks,

I'm in the process of installing a new vanity top. pulled the old vanity top/sink out and have the new cultured marble top in place. The drain hole, of course, doesn't line up. I need to move it back about an inch. No problem, just use a repair fitting.

I grab one and get ready to cut/install and I see that somebody's already beaten me to it and the existing plumbing has a repair fitting place. With not much pipe to work with i have no alternative but to cut out the old one and replace it. Heck, it's about an inch or so so my hole/tail pipe might just line up.

Here is the issue.

The pipe coming out for the horizontal run from my ptrap is now only about 3/4 of an inch. If I bury this in the repair fitting it's OK but of course my tail pipe doesn't line up straight with the ptrap. If I insert it only about 1/2 an inch, my tail pipe lines up nicely but, of course, the horizontal run from the ptrap is no longer buried in the repair fitting.

I see the following as my options:
1) insert the ptrap the 1/2 inch so that it all lines up. Cement in place.
2) build a whole new ptrap.

Frankly, I'd much rather go for 1) if it will be sufficient. Will a pipe inserted the 1/2 inch into the repair fitting be leak proof and sufficiently strong?

Something tells me that 2) is the way to go but I doubt that, being a novice, I can get the new ptrap assembled and installed so that it fits as perfectly as the existing one.

I'd go for confidence rather than wishful thinking. It won't cost much to redo the p-trap. Anytime fittings are barely holding on, even if cemented would leave me with a fair amount of burden that I am not willing to bear.

Somewhere in the code it says that the pipe shall be fully inserted into the fitting.

Seems like a good rule of them is insert it the same diameter as the male pipe's width. Surely there will be exceptions.

Disregard the above statement ^^^
More I thought about it, I don't know what I was thinking!

Thanks for the input folks.

Ran down to homers and the parts to build a new one cost all of 7 bucks.

Now all I have to do is cut/cement it properly.

Have a great weekend.