i have a porter cable 12 1/2 planer which does a good job but i am wanting to upgrade to a better one,,i was thinking about the g0815 grizzly planer,,,some of my concerns are its a 3 knife system and i was wandering how hard it is to change the blades,,my porter cable was 2 knife but there was no adjustment,,,you just removed the old ones and replaced with the news ones,,plus they were double edged,,i know this planner isnt like that,,so can anyone tell me how much trouble it is to replacing the knives,,i was also looking at the spiral cutterhead and was also wandering about how hard it is to replace,,i know alot of people will say just get the planer with the spiral head but the weight of the planer is a big concern,,its nearly doubled to get the spiral cutterhead,,can anyone give me some input on this,,,,and i have also thought about getting a 13 inch spiral cutterhead benchtop planer,,but i was really wanting the extra 2 inches,,,,