What's with the name of the mod?

A pipelayer is a person who installs ("lays down") pipes in underground areas. It is also a reference to the separate underground layer where the belts are routed.

Isn't this a little bit cheaty?

Yes, it absolutely is! The straight-line and length limitations of standard underground belts are part of Factorio's design challenge. Overuse of this mod may result in an unintended shortage of spaghetti in your factory.

On the other hand, you still have to move items on the surface to split, balance, and route items into and out of assembling machines, so the potentional for abuse is somewhat limited. Using this mod also introduces a new layer of complexity, where keeping track of where items are routed is no longer obvious just from looking at the surface. If you're not careful, you can make your own factory layout very confusing to navigate.

My belts aren’t backing up! Where are all my items going? Are they getting eaten by Beltlayer?

By default a beltlayer connector buffers up to 4 stacks of items in hidden chests. If you are running mods that increase stack sizes, this can be a lot of items, but nothing should be lost.

There is a mod option to show the hidden chests, allowing you to directly insert/remove items for the buffers, or just see how items are inside. There is also a mod option to change the number of stacks to better suit your mod setup.

My sushi belts are backing up after just a few items, and not flowing smoothly or at full throughput. What’s going on?

Each connector has two buffer chests, one above ground and one below. Each chest holds two stacks. If you have many different item types on a belt, this won’t be enough to buffer items between scripted transfers.

You can use the mod options to increase the number of stacks per buffer chest, but this increases the number of buffered items for belts handling only a single item type. You can use the mod option to show the buffer chests, and set different stack limits for each with the standard “Red X” interface if this is a problem for your factory.

Alternatively, you can change the mod options to transfer items between layers more often by reducing the transfer period, but this will increase UPS costs.