So you want first hand experience with half-axed battery charging?
Like Flux said, I don't think you will exceed the maximum amps very long. Probably less than 20 seconds. Maybe less than 5 seconds.
I personally would not want more than 8A charging that battery for more than a few minutes (10 minutes?) either way.
The surface charge will come up to the system voltage very quickly, and the charging current will drop.
You don't say how you will charge the battery while driving.
A lighter socket jack into the lighter socket will have plenty of voltage drop, if the wire from the lighter to the battery is marginal, say 16 gauge and 6~8 feet long. The voltage drop with a low battery will limit the amps at that time, but as the SLA reaches a higher voltage the current and voltage drop will be less, allowing the battery to reach the system voltage in a semi-controlled fashion.
I would recommend a couple things...
Like `car charging' the battery every morning for a few minutes if the battery is below ~12.35V or if the battery will be heavily used that day. Get it up past 14V for a couple minutes, then let the solar finish it.
And lots of spare fuses for the lighter fuse. Just in case.
And don't use `genuine store-bought jumper cables' from battery to battery. Something like 8' of #16 would be OK, and they could be a good way to get the SLA up near system voltage before using the lighter plug, if the lighter plug is blowing fuses.
And don't let the SLA battery get warm while charging. Same for the wires.
Hope it makes sense,
G-