Need help trying to make a hole bigger

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I’m on my phone now so can’t look at your model, but if it is the same one I looked at earlier you are probably having problems because it is very small.
Have a look at using the dave method to make things large enough to work with.

The Dave Method

The Dave Method is the clever use of components popularized by @DaveR to avoid the tiny face issue. Sketchup fails to form faces when edge segments get down around the 1/1000" mark. However, tiny faces can exist so the workaround has generally been to scale up your geometry, edit it, then scale back down. This works, but can lead to some issues. The Dave Method leverages the power of components to make life easier. The basic concept is, you start with a component set at the size you want, t…