There are a number of ways to measure a recipient.
Once you have the measurements, you can use one of these techniques for calculating the proper scale.
Here is a video tutorial series based on the Blender method of sizing and scaling. Thanks to Peter Binkley for this. https://www.youtube.com/playlist?list=PLBHsuyNYSpxs4Xqj4_kzcbBiSby2tKqrH
Here is a short guide that describes using a spreadsheet: https://docs.google.com/document/d/1vWDoGMzwca5G__8-2kdTte2w3qs8-h_Nv7PmFLszn4w/
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