This may be a little off subject, but what about faking other things on your time slip such as return visits and Bible studies? I for the most part did honestly report these other statistics accurately along with my time accept for my last year but I think this area may be even more skewed than hours. I remember when I was a regular pioneer and I had on a regular basis 5 Bible studies a month.
The C.O. came to our hall and said that I was doing a good job but then this other reg. pioneer elder in our hall who had been to Bethel tried to discredit me by saying that my actual Bible studies were more like 2 because I only met with certain Bible studies twice a month and not every week. I guess technically there are all these rules about how to report studies and return visits like you can't count an RV until the third visit, etc. but the average publisher or even pioneer doesn't know the exact rules. Plus, it's not like anyone goes over the rules ever, thus I suspect widespread inaccuracy on this data, maybe even more than time. But hey, if you can't count time accurately, what else can't you count?
I must admit that towards the end I would try to compesate my low hours but beefing up other things like say throwing in a few extra R.V.'s. So, my time slip might say only 5 hours, but look he has 20 return visits, wow, that's quality not quantity.