By now, even the giants on Earth were too small for Gohan to even notice. Which is part of the reason why he didn't see when Goku used his instant transmission technique to appear behind Gohan just before he used the gun again.

Proportionality there was no change in their hight, but overall they both went through their biggest growth yet. Gohan loved the feeling of every muscle in his body expanding it was a high that could not be compared to anything else. This round of growth started with him about the same size of the Earth, slowly to Gohan his body expanded out further and further. At this point he was growing thousands of feet per second, but to his massive body that wasn't much.

His form stretched out with his head and feet extending past the earth, it continued while so much that now the Earth would only be level with Gohan's abs. As his latest round of growth finished Gohan decided it was a time for a little more "fun" before he got even bigger. He let the gun go, within arms reach so he could use it when ready and turned to face the Earth again. He was amused by the sight of how small it was to him now.

What Gohan didn't see was that Goku had again used his instant transmission technique to transport himself where the gun was.