JR, I agree with most of what you are saying, but the statement that anything less than 20A - for 100 AH battery - will result in "too low" charging voltage, is way too strong.
0.2-0.3C is an "optimal" current for most flooded batteries, not a "minimal" current. You can charge it with 6A if you like. This is what 100W panel will do, and it will bring 100 AH battery to 99.999...% by the end of the day, or next day, depending on how deeply it is discharged. The last few hours it will run less than 6A of course, being on Float.
