Correct. There's a point that needs to be made in using SCUBA tanks as an HPA fill source lakeside. Once the SCUBA tank pressure drops below 3000psi, each subsequent fill will be less than the one before. The pressure drop is dependent on the size of HPA tank being filled and number of fills going on. You could stretch the available full pressure fills somewhat by using a 4400psi SCUBA tank. One forum posting I reviewed stated that ten fills of a 68ci paintball tank will drop an 80cf SCUBA tank down to 1000psi. So basically, an HPA fill using a SCUBA tank will give ever lower pressure fills over the day. A CO2 fill station will give consistent fills during the day.
One trick I've seen for HPA fills is to use multiple tanks. One for a base fill, then a second to top it off. The top-off requires less gas than the base fill, so that tank's pressure drops slower and you still get a good charge. Once the base fill tank runs low, the top-off tank becomes the new base fill tank and you go get a new top-off tank. The downside is that you need several scuba tanks and two fill stations to do this.
