Reaper - track-by-track syncing issues (noob question)

I'm new to Reaper and am trying to assemble a track using wav files. I have the drums and piano to start with. Reaper likes to throw in a fade in and dead space before my samples start, which is messing up the timing. After 4 bars, the piano starts to leave the beat, and by the end things are especially screwed up because neither loop properly. I used to work with Acid, and Acid would never do this - as everything stayed on point. I don't want to go back to Acid, because I like Reaper, but like I said, after 4 bars everything gets thrown off. I know my drum sample is trimmed perfectly, but for some reason, this dead space in the beginning throws off the timing of that alone. Granted, it's by a miniscule amount, but I don't want anything thrown off. Does anyone know what I'm referring to?

check the auto crossfade options - you might have something weird in there. maybe set the overlap to 0. also, check that your default item mode is "beats, position, length" (in the project properties - alt-enter), turn on snap to grid (two options in the toolbar), and then you can alt-drag the edges the lock to grid. with those options all on, you should be able to dynamically change the tempo etc a'la acid.

Fade In: Options->Preferences->Project->Defaults Here, under Items section you'll find Fade length. Set it at 0:00:000. Dead Space: Options->Snap/Grid Settings... or simply click on toolbar icon Here, under Snap Settings section you'll find this option: Snap media items apart by: (___). Set it at 0:00:000 or uncheck this option.

Awesome. Thanks! Out of curiosity - what purpose does "snap media items apart by ___" serve normally? There are so many settings here and it's a little confusing.