Ah, but it all goes back to Mawhonic, doesn't it? Mawhonic's height, much like Nien Nunb before him, is debatable. It looks to me like he's actually not supposed to be tiny.
The character itself was portrayed on-set by a full-height actor, Danny Wagner, an ILM modelmaker and makeup artist who appears on many of the Blu-ray special features. I don't know how tall he is, but the Mawhonic costume was later reused in the Nightlander Club as the oh-so-imaginatively named Nic Whoma
, and based on Wookieepedia's cruddy photo, it looks like Nic is of average height. So, in reality at least, Mawhonic was regular-sized. Hasbro's Mawhonic figure - released twice last year - stands as tall as young Anakin, meaning he's somewhere between one and two feet shorter than a regular-height human. Of course, Mawhonic could have been scaled down digitally in the film - but was he?
First off, there are several Gran that walk through the background of TPM, and they're all at full human height. Whether or not you can ascertain the height of the Gran senators in TPM (including Aks Moe - and I always thought they were full-height), Ask Aak is of similar height to Bail Organa in AOTC. These ones in the hangar are on the same plane as the Gella girls and the Nikto to Watto's right.
So who are these guys? It's hard to make out the details, but they don't dress like Mawhonic, so we can assume he's not one of them. It's likely that they're Mawhonic's pit crew - they're not near his pod racer here, but they are dressed fairly similarly to the Gran that are standing near Mawhonic's pod racer before the race. The compisiting is odd, but the two Gran near his pod racer look to be the same height as he is.
Here's a wider shot, comparing the sizes of the pod racers. Mawhonic's is in the lower right of the shot, in the front row, and Anakin's is in the the middle of the second row. Anakin's is the smallest, and Mawhonic's is taller, though not the tallest one there. The two figures near Mawhonic's pod look to be around the same height as other characters in the shot, and they are the same height as the Gran that was standing directly next to Mawhonic's engine in the last shot I attached.
Here's a shot of Anakin standing next to the engines.
Here's Mawhonic with Anakin's engines behind him.
These last two shots are filmed from different angles, but it's still pretty clear that Anakin is supposed to be shorter than the engines at this point and Mawhonic is supposed to be taller.
It looks to me like Mawhonic was supposed to be normal-sized, but someone somewhere decided after the film was done that he should be the same height as the rest of the racers. Digital compositing can be tricky business, but I don't think he was scaled down much, if at all. Maybe he's supposed to be a little shorter than the average Gran, but not by a lot. I believe that he - like Nien - was robbed of his full stature for no good reason.