Aggressive bidding pays

At Oxford I lost sessions 3 and 4 to Nick Wedd, playing in the same seat at the other table. The reason seems to be that my bidding was overall more cautious. What would you do with the following hands?
(3/1) Vorhand: J:C H, C10, S:A Q, H:K 8, D:K 9 7. I passed when M bid 18. Nick played 18 (quite likely M passed - he doesn't really have a bid), found the DA and made.
(3/7) Mittelhand. J:C S, C:K 9, S:8 7, H:Q 7, D: A 9. I passed and would do so again, but Nick bid 18 and made a club contract (CA and D10 in the skat).
(3/15) Mittelhand. J:S, C:A K 9, S:-, H:10 Q, D:A K 9 8. I overcautiously passed, fearing small spades in the skat. Nick bid 18 and found a jack and a ten and made schneider in diamonds.
(4/11) Mittelhand: J:S H, C:7, S:Q, H:A Q 9 8, D:Q 7. I passed, having nothing outside hearts. Nick bid 18, picked up CQ, C8 which looks pretty unpromising, but somehow managed to win a heart game.
(4/21) Vorhand: J:C S, C:9 8 7, S:10 K 8, H:-, D:K Q. I passed when M bid 18. Nick played 18 (maybe M passed?), found two diamonds and made.
It wasn't all one way. Nick lost a few marginal games, and there were some he didn't bid, but on balance he came out ahead.
(3/22) Hinterhand. J:D, C:K, S:A K, H:10 K 9 7, D:K 9. I passed, but Nick bid to 22 and had to give up a Null on finding SJ in the skat.
(3/23) Mittelhand. J:S H, C:7, S:A 10 9 7, H:9 7, D:A. Nick stopped at 23, but having only one danger card to get rid of I bid on and bought the contract for 27, planning to try a grand if I didn't get the cards for my null ouvert. The skat was CQ, H10 so the null ouvert was in fact safe.
(4/5) Vorhand. J:C, C:A 10 7, S:Q 7, H:10 9, D:9 7. I passed H's bid of 18. Nick played (maybe H passed) but found SK, DQ and lost.
(4/10) Vorhand. J:C H, C:Q 9, S:10 K 8, H:A Q, D:Q. I passed M's 18. Nick played (maybe M didn't bid, though his hand looks quite good) and lost, even though he found a spade and a heart in the skat.
Maybe this is all just luck, but I think I will try bidding slightly more of the marginal hands next time I go to Oxford.
(3/1) Vorhand: J:C H, C10, S:A Q, H:K 8, D:K 9 7. I passed when M bid 18. Nick played 18 (quite likely M passed - he doesn't really have a bid), found the DA and made.
(3/7) Mittelhand. J:C S, C:K 9, S:8 7, H:Q 7, D: A 9. I passed and would do so again, but Nick bid 18 and made a club contract (CA and D10 in the skat).
(3/15) Mittelhand. J:S, C:A K 9, S:-, H:10 Q, D:A K 9 8. I overcautiously passed, fearing small spades in the skat. Nick bid 18 and found a jack and a ten and made schneider in diamonds.
(4/11) Mittelhand: J:S H, C:7, S:Q, H:A Q 9 8, D:Q 7. I passed, having nothing outside hearts. Nick bid 18, picked up CQ, C8 which looks pretty unpromising, but somehow managed to win a heart game.
(4/21) Vorhand: J:C S, C:9 8 7, S:10 K 8, H:-, D:K Q. I passed when M bid 18. Nick played 18 (maybe M passed?), found two diamonds and made.
It wasn't all one way. Nick lost a few marginal games, and there were some he didn't bid, but on balance he came out ahead.
(3/22) Hinterhand. J:D, C:K, S:A K, H:10 K 9 7, D:K 9. I passed, but Nick bid to 22 and had to give up a Null on finding SJ in the skat.
(3/23) Mittelhand. J:S H, C:7, S:A 10 9 7, H:9 7, D:A. Nick stopped at 23, but having only one danger card to get rid of I bid on and bought the contract for 27, planning to try a grand if I didn't get the cards for my null ouvert. The skat was CQ, H10 so the null ouvert was in fact safe.
(4/5) Vorhand. J:C, C:A 10 7, S:Q 7, H:10 9, D:9 7. I passed H's bid of 18. Nick played (maybe H passed) but found SK, DQ and lost.
(4/10) Vorhand. J:C H, C:Q 9, S:10 K 8, H:A Q, D:Q. I passed M's 18. Nick played (maybe M didn't bid, though his hand looks quite good) and lost, even though he found a spade and a heart in the skat.
Maybe this is all just luck, but I think I will try bidding slightly more of the marginal hands next time I go to Oxford.