I recently compiled NetSurf 3.9 on Linux and it was pretty bloody slow even on my PC so maybe the problem is that NetSurf has simply got too much for low powered machines?
Unfortunately this tends to happen with large open source projects as more features are added it becomes harder to run ports on older machines, ScummVM is a good example of this (try running version 2.1 on an 030!).
I appreciate your AmigaOS porting efforts Chris