doco -

like Crispi, I only use 120 gph pump for recirculating, but I'm running 12 buckets. If it's good for 4 and good for 12 it will probably be good for your 8.

With a stronger pump, you also run more of a risk with quicker water movement that the "new" water wouldn't make it into those "T's" into from the main water line. Having less GPH means less negative pressure in your connecting lines, and a higher likelihood of the contents of the bucket circulating out, IMO. I wouldn't worry about having two holes in the bucket, with just one hole my ppms and phs stay fine, especially with the $1.39 shutoff valves from the reservoir.

how big is your reservoir? can you have the 9th bucket with the pump in it at a lower height than the rest of your growing buckets? As long as you have a height difference and a good sized res, you shouldnt even need float valves or texas controllers or anything like that, at least I didn't. With 12 buckets and 6th week of bloom, you can still skip 2-3 days without topping off -- can't beat that.

It's weird that GH doesn't sell the HF with simple netpots instead of that top bucket, the more holes the better IMO, especially if you're doing a DWC hybrid.

3 gallon netpots: $3
5 gallon black buckets: $5
GH HF kit: $12

for anyone-
for 20 bux each you can DIY a HF that'll work great. All u need is a good strong air pump for about $60 that can power up to 16 farms. 8 x $20 + $60 + $10 for 1/4 inch tubing and fittings and you've got a 8 piece high performance HydroFarm for $230. For another $20-$30 you can make it recirculating. Not to mention that you can get a 50 gallon reservoir from Target for about 8 bucks, instead of the 13 gallon res that comes with the pre-packaged 8x setup. For those without a hydro store near them you can't beat the convenience of the pre-packaged deal, but DIY-ing will save you money and get you a higher-performance system in the long run. My local store will even drill all the holes for you and give you a 10% discount on everything, plus no shipping $.