@Poxicator: How do you define powerfeeding? Feeding to satiation or abdomen / carapace sze relation? In other words, when does healthy feeding become overfeeding?

I think that's answered rather simply by "when that is the intention".

Power feeding is providing as much food as the T will eat with the intention of rapidly developing the T to get through successive moults.

Stanley Schultz suggested 3-5 crickets (equal to the size of the abdomen) per month is enough food to maintain a tarantula. Ive personally known of people who think that amount is fine as a weekly feed, and others who feed on a daily basis! I tend to feed once a week, 1 cricket/roach and Im not bothered by missing a week. However I do tend to pay more attention to the slings.

The best guide I can give is how rounded the abdomen is which neednt be that much bigger than the carapace.

Power feeding is a load of bull, when i 1st got into the hobby i also wanted to power feed, the fact of the matter patience is key you still going to have to wait 2 or more years depending on the species to get a descent sized spider.

I have personally noticed hardly any difference in growth rates with over feeding your spiders.

If you want to get the best results and not wait your money and over feed your spider.

3 crickets a week is more than enough depending one the size of your spider. There is no fixed formula. As i said the size of the spider, size of the food your spider will eat and so on...... i feed my big girls 15 large crickets in one feeding and this is done every 2nd week. i feed my slings 2 large cricket a month, crush the crickets head throw it in and ul see your sling will eat on the cricket for 3 days until it cant eat any more.