I own a 510 and paddle it in short choppy conditions. (no experience of other surfskis.)
I have noticed that it is important to paddle early to catch the bigger waves (3-4 ft). Put the effort in early, get speed up. Then let yourself 'ride up' the wave.
If I wait for the wave to pick me up, then two things happen. One is that I start to broach (the 510 has a large rudder which really catches the water). The other is that it is very hard to get speed up, the crest reaches the cockpit and I flood. I'm about 86kg in my kayak gear, so a bit lighter than yourself.
I think that the 510 is a very stable ski - I can paddle broadside on to very steep chop quite comfortably.
Downwind is actually more challenging, and I think it is due to the need to 'catch' the wave by accelerating early.
The rocker on the 510 sweeps up a lot toward the stern. This, combined with the large rudder, increases the tendency to broach when water is moving past the boat (stern to bow).
[edit]
Looking at the profile of the v7 vs 510 on this page
surfskicomparison.com/ (this is a fabulous resource), it is very apparent that the 510 has most of the total rocker in the section sweeping up from midway to stern. The v7 has a bit less total rocker, but it is distributed more evenly.
Also, the v7 has more volume in the bow - the 510 is more towards the stern as previously stated.
All of this combines to make the 510 a ski that turns very very quickly, but is prone to broaching. A broach is quite hard to deal with (one of these resulted in the first and only time I've capsized).
My suggestions, based on my experience are:
- If you feel yourself getting too high on the way, starting to swamp, let the wave go. Immediately after the crest has passed, dig in, paddle hard, to catch the following wave.
- Watch out for a broach, push those pedals hard and early.
- Start your wave-catching sprint early - the 510 is a slow, heavy boat, so it will take longer to get up to speed. You can only reliably catch waves if you can match speed with them. The bigger the wave, the faster it moves (well, wave speed is dependent on wavelength).
- Sometimes, it is better to paddle beam-on to waves for a bit, then go straight downwind. With very short steep waves, trying to surf across them can be difficult.