When I started helping my friend with her plaster pool (plaster 22 years old) she had no CYA and her pool guy had been using CalHypo, only, forever and she had constant green algae. Her CH was 700 but her TA was pretty low. Basically all I've done was add CYA and had her start using bleach. And run the pump 24/7. For several weeks her pool has been pristine, no algae, AND her CSI was -0.02 last time I checked it and pH has remained steady for a month at 7.5.
So even with a high CH 700 I personally have been witnessing how a pool can be managed with too much CH. We'll get the CH down over time. I'm not advocating, out of control, high CH, by any means.
If CalHypo is the only thing you can get in quantity then seems like a reasonable alternative. Don't let it sit on the bottom in any pool.
There is a really strong correlation between TA and CH so put figures in to The Pool Calculator to see what would be the maximum amount of CH you would want to put in you pool with your current TA level. That will help you to keep from over doing it with the CalHypo in terms of CH.
I've used CalHypo, on and off over the years. My friend and I would split a 100 bucket. VERY IMPORTANT - Store the CalHypo bucket where it will be least likely to have moisture or rain on it. If moisture gets into the bucket it can become as hard as concrete and the fumes, when you open the top can knock you over. Carry the bucket outside, out of enclosed area, when you open it and keep your face away from the top. When you are scooping it out take care to not let any moisture get in the bucket.
gg=alice